CHAPTER V.

CHAPTER V.THE DISTRIBUTION AND CONSERVATION OF SOLAR ENERGY.What, then, becomes of the light and heat flashed forth with eternal energy from the fiery waves of the sun’s incandescent atmosphere? Professor Ball (“In the High Heavens”) says, “Much of what has been said with regard to light may be repeated with regard to heat. We know that radiant heat consists of ethereal undulations of the same character as the waves of light. Hence we see that the heat or the light radiated from a glowing gas is mainly provided at the expense of the energy possessed by the molecules in virtue of their internal oscillations.” Conversely, of course, the ethereal undulations thus induced by high molecular motion in the heated gas or vapor must disappear in so-called absorption or transference by contact with other molecules, themselves devoid of such specific internal oscillations. The heat motion then disappears as heat by its conversion into work, just as the motion of a belt in a mill disappears in the work of the machine which it drives. One two-hundred-and-thirty-two-millionth part of the radiant solar energy, we know, is caught by the flying planets of our system in the forms of heat and light, adapted to sustain life and its continuedpotentiality, and we know that this solar energy is the sole source of all the development and maintenance of the planets as the possible abodes of organic life, past, present or future.But what of the vast total, of which we consume so minute a fraction? It is true that, in addition to the planets, space is occupied by many small meteoric bodies, which manifest themselves to us as shooting stars and meteorites, but the mass of these is too trifling to be estimated. Professor Helmholtz, in his “Popular Scientific Lectures,” says, “According to Alexander Herschel’s estimates, each stone is, on an average, at a distance of four hundred and fifty miles from its neighbors.” When these bodies enter our atmosphere by force of the earth’s attraction they are heated by its atmospheric friction to incandescence, and in most cases are even volatilized before reaching the earth’s surface. The vast volumes of solar heat and light, however, are poured forth from the sun indiscriminately in all directions into illimitable space, wherein all the masses of concrete matter, including the stars, are relatively far less in volume than the flying motes of the purest morning air which sparkle in the flood of light sent forth by the rising sun. Is all the rest wasted? Professor Balfour Stewart, in his work “The Conservation of Energy,” says, “If this be the fate of the high-temperature energy of the universe, let us think for a moment what will happen to its visible energy. We have spoken already about a medium pervading space, the office of which appears to be to degrade and ultimatelyextinguish all differential motion, just as it tends to reduce and ultimately equalize all difference in temperature. Thus, the universe would ultimately become an equally heated mass, utterly worthless as far as the production of work is concerned, since such production depends upon difference of temperature.”It is obvious that the starting-point taken by the author last quoted, but which, nevertheless, is in accordance with the views now generally prevalent, is diametrically opposed to that sought to be established in this work. Professor Stewart takes the sun’s inherent energy as the initial point of departure, and reasons from that as to the final consequence when all its light and heat shall have been distributed or dissipated into the attenuated medium which occupies space, and which will be thus slowly heated until all space has been raised in temperature to that of the last dying sun, when all will thenceforth remain unchanged and unchangeable, silent, dark, and dead, to all eternity. On the contrary, the purpose of the present work is to establish a directly opposite principle, based, however, on demonstrated scientific facts and not on theory, that the medium which pervades all space was originally in the same equally and universally potential state (with its molecules raised to a tension constituting an unstable equilibrium) in which, practically, Professor Stewart’s argument leaves it finally, and that this universal molecular energy of position was permanently maintained by the employment of the forces which afterwards,transformed into light and heat, were shed abroad by the sun in the work of again overcoming the intermolecular tension of cohesion, and that the light and heat of the sun are merely caught up again by these same or other molecules and successively employed in the same manner, while the planetary electrospheres utilize these same forces of internal tension in the generation of electricity, which, sent to the sun, is converted into light and heat, and these are again transferred to their original source. The rotation of the planets is the grand exciting cause, and the process, in its complete cycle of development, has live stages: first, planetary generation; second, transference by currents of electricity to the sun; third, conversion into light and heat; fourth, emission; and, fifth, reabsorption and conversion again into molecular energy of position. All space is thus found to be pervaded by extremely attenuated vapors, which contain the elemental constituents out of which suns and planets are evolved under favorable circumstances of development, and, among other vapors, aqueous vapor, and that these are the agency upon which the planetary electrospheres operate in their generation of electrical currents, and which vapors, in turn, by absorption of the solar energy of radiation, again transform this energy into mutually balanced electric potential, until it is once more disengaged as electricity by the rotating planetary electrospheres, and so on in a constant circuit forever repeated. It differs from perpetual motion, however, in that the planetary rotation is the externaland not the internal generative cause, since the electrical forces neither cause nor control these motions; they belong to the realm of gravity. The disassociation, moreover, is electrical and not chemical disassociation. The tensions are against cohesion and not against chemical affinity; are, in fact, similar to those which constitute our atmosphere a vast electrical reservoir; and the aqueous vapors, through all their changes, permanently remain as aqueous vapors, except those condensed portions disassociated by electrolytic action at the electrospheric poles, and which have no relation to the attenuated vapors of space, except in that the latter are their sources of supply. The process is analogous to what we see around us at all times in the atmosphere. While the process described by Professor Stewart resembles the emptying of the inherent water of a cloud, in the form of rain, into an ocean which never yields up its water again, so that, when the cloud has rained itself out, it is gone forever, the processes here sketched are like the vapors which are caught up by the heated air, carried over the thirsty lands, distributed in rain to fertilize and vivify them, then gathered in a thousand tiny rills from countless fountains, again descending to the sea and again carried up in vapor, and so on over and over in unceasing round. It is the difference between an old-fashioned flintlock musket and a modern magazine rifle, except that the magazine is always full.This great ocean of space was primordially charged with these potential vapors; it is theconstitution of space itself. We are so accustomed to consider space as empty, and that it is nothingness, the antithesis of something or anything, that it is a negation or a blank, that it requires an effort to even think of it as a fully stocked establishment with all the goods necessary for use or ornament, in the latest styles and of prime quality, only not made up, and that all our suns and worlds are merely tailoring establishments where the operatives cut and fit and make them up to order. When more goods are wanted they have to go to the store.Is space, then, eternal, and is this constant round of energies to be eternal? If one is eternal, so is the other, and surely nothing can be more eternal than space, and we cannot conceive of any other space than this space. Out of it came all created things, and so long as the orbs rotate without retardation, so long will these interchanges go on without impairment, and that they do so rotate is the necessary corollary of the fact that they ever began to rotate. If rotation, on the contrary, was imparted by special creative power, then the same power established the laws by which they rotate, and took cognizance of resistance as well. Whatever the impulse was, it still remains; whatever caused the rotation to begin maintains it; if the cause is eternal the rotation may be eternal; and, in any case, its period must be measured by cycles of æons, to which the allotted lifetime of a dying sun—a few million years, perhaps—is but as the sunburst of a morning-glory flower to the hoary age of a mighty planet. Compared with the popularview of the sun’s life-period, we may formulate the terms of an equation in which the sun’s mass, compared with the realms of infinite space, is as the sun’s lifetime—on a basis of contraction of his volume—to the lifetime which actually is to be. As one of the terms is practically infinite, so must be the answer to the problem. Professor Stewart says, “We cannot help believing that there is a material medium of some kind between the sun and the earth; indeed, the undulatory theory of light requires this belief.” It has already been shown that the transmission of electricity also requires it, but that there must be a medium quite different from the undulatory ether. Professor Proctor (“Mysteries of Time and Space”) says, “We may admit the possibility that the aqueous vapor and carbon compounds are present in stellar or interplanetary space.” Again he says, “Assuming, as we well may, that space is really occupied by attenuated vapors.” The same writer says further, “To this end all thoughtful study of the mechanism seems to tend (associating, perhaps, our visible universe with others, permeating it as the ether of space permeates the densest solids, and in turn with others so permeated by it); there may be that constant interchange, that perpetual harmony, of which Goethe sung:‘Balanced worlds from change defending,While everywhere diffused is harmony unending.’ ”The light and heat poured forth from the sun are, as stated, in the form of radiated energy.They penetrate the attenuated vapors as far as vision extends, and doubtless farther, but they cannot reach the boundaries of space, for even the mind of man cannot reach those limits. Aqueous vapor absorbs heat; we know this without any demonstration, for the radiated heat of the earth is arrested by a veil of clouds, so that on cloudy nights frost will not form. So also the sun shining into water will raise its temperature, as in a glass globe, and such absorption of heat by aqueous vapors or water would be much more manifest were not a large part employed in loosening the tension of the constituent molecules, since, when thus employed, it is not manifest as sensible heat. Professor Tyndall, in “The Forms of Water,” states that “The quantity of heat which would raise the temperature of a pound of water one degree would raise the temperature of a pound of iron ten degrees.” Professor Stewart, in “The Conservation of Energy,” says, “That peculiar motion which is imparted by heat when absorbed into a body is, therefore, one variety of molecular energy …. Part of the energy of absorbed heat is spent in pulling asunder the molecules of the body under the attractive force which binds them together, and thus a store ofenergy of positionis laid up, which disappears again after the body is cooled.“Heat will only be changed into work while it passes from a body of high temperature to one of low …. At very high temperatures it is possible that most compounds are decomposed, and thetemperature at which this takes place, for any compound, has been termed its temperature of disassociation.Heat energy is changed into electrical separationwhen tourmalines and certain other crystals are heated.” It may be added that it is also changed into electrical energy by the operation of all electrical machines, as molecular motions are all mutually interconvertible, and heat itself is only a mode of such motion. Of radiant energy, the same writer says, “This form of energy [radiant heat] is converted into absorbed heat whenever it falls upon an opaque substance … and heats it. It is a curious question to ask what becomes of theradiant lightfrom the sun that is not absorbed either by the planets of our system or by any of the stars. We can only reply to such a question that,as far as we can judge from our present knowledge, the radiant energy that is not absorbed must be conceived to be traversing space at the rate of one hundred and eighty-eight thousand miles a second.”We know, of course, that aqueous vapors are partially opaque to heat rays, as the radiated heat of the earth is partially arrested by such vapors in the atmosphere, but they are apparently transparent to the rays of light. But we know that this cannot be entirely true in fact, for light rays only differ from heat rays in the comparative length of their waves or impulses, while rays of light are always accompanied—when emitted by a thermally incandescent body—by a much larger number of those of heat. As a body is raised in temperature radiant dark rays first appear; these being raised higher, becomevisible as light, and new dark rays are radiated behind them, and this continues till after the state of highest incandescence is reached and the invisible chemical rays beyond the spectrum appear. It is like a crowd surging forth in flight from the doors of a building; as the speed of those in front increases to a run, others follow more slowly in the mass, and as these gain speed others continue to follow, while the great mass of laggards still trails along in a lengthening line to the rear. The perception of light is itself merely due to the constitution of the optic apparatus of the observer, which only takes cognizance of vibrations radiated from the middle portion of the scale, just as the ear does with sounds, and not to any actual difference in their mode of production. That heat rays and light rays are identical in constitution can be readily shown by the experiment described by Professor Tyndall in his “Forms of Water,” in which an opaque screen of iodine solution in bisulphide of carbon was employed to arrest, in a beam of light, all the light waves (to which it is entirely opaque), while transmitting the dark rays. These non-luminous rays are then converged by a lens: “Let us, then, by means of our opaque solution, isolate our dark waves and converge them on the cotton. It explodes as before …. At the same dark focus sheets of platinum are raised to vivid redness; … a diamond is caused to glow like a star, being afterwards gradually dissipated.” Sir William Herschel (see article “Spectrum,” Appleton’s Cyclopædia) says, “If we call light those rays which illuminateobjects, and radiant heat those which heat bodies, it may be inquired whether light be essentially different from radiant heat. In answer to which I would suggest that we are not allowed by the rules of philosophizing to admit of two different causes to explain certain effects, if they may be accounted for by one.”… “Tyndall, by similar experiments, found that the thermal energy of the invisible radiation of a very powerful electric light is eight times that of the visible …. Seebeck showed that the position of maximum heat in the spectrum changes with the nature of the prism and sometimes occurs in the red.” Melconi, with prisms of alcohol and water, found it in the yellow. Athermic bands are also found in the heat-spectrum, corresponding to the Fraunhofer lines seen in the visible spectrum.We may illustrate this successive development of more and more rapid light-waves by conceiving of a harp having musical strings of various length and thickness, but not strung up, so that, when swept by the hand, the vibrations are felt, but no musical tones are produced. If, now, all the strings are simultaneously and gradually stretched while under continuous vibration, we will first hear the hum of the lighter strings, but deep down in the scale; and as the tension gradually increases the pitch of these will rise higher and higher and be succeeded by other new tones below, until the whole register is simultaneously sounded. And if the tension be further increased, the vibrations of the upper strings will gradually grow so rapid that the ear can take no cognizance of them, correspondingto the invisible chemical rays of the spectrum, while the middle strings will be sounding loudly, and others will be slowly vibrating below the musical scale, but without sound, corresponding to the invisible heat rays. In addition to this gradual ascent of pitch along the scale, however, there is reason to believe that sympathetic vibrations are induced in the spectrum of thermal and chemical light corresponding to the over-tones in music and to those hidden rhythms which differentiate the “timbre” of one kind of musical instrument from that of another, so that a definite wave-length will not only repeat itself among adjacent molecules, but will give rise to harmonious vibrations quite different in amplitude and velocity. An example of this is found in some of the phenomena of phosphorescence and fluorescence, in which chemical rays totally invisible are able, under suitable conditions, to excite molecular movements corresponding to parts of the visible spectrum, and quite different in wave-lengths and in rapidity. This process is precisely the converse of what we perceive in thermal light; in the latter case the colors ascend, loaded with invisible heat rays; in the former they descend, loaded with invisible chemical rays, only noted, perhaps, by their actinic action on the photographic plate. Others, as the sulphide of calcium paints and the like, repeat their own vibrations for many hours, and we find in certain chemical salts of some rare metals, as lanthanum and cerium, the curious property of suddenly raising the whole scale, as in a recently introducedgas-lamp, in which a skeleton mantle of these oxides glows with a wondrously beautiful white light under the relatively low temperature of a small Bunsen burner; similar phenomena are manifested in the behavior of electric discharges in attenuated gases, as well as in what is known to children as “fox-fire,” wood undergoing slow decomposition in damp places, or in the self-luminous secretions (corresponding, perhaps, to ptomaines or like products) of glow-worms and other animals. If we ever—as we probably soon shall—reach that point where we can illuminate our dwellings with “cold candles,” as the inhabitants of tropical countries carry about a few fire-flies in a paper box for a lantern on dark nights, it must be by the study of these phenomena. But meantime “Old Sol” will continue to discharge his accumulating stores of both heat and light, for both these are essential, not only for use upon the planets, but throughout all the realms of space. In the transformation into and emission of his radiant energy the sun is not a chemical engine, but a mill,—one of those which “grind slowly, but they grind exceeding small.”The difference between radiated thermal light and heat is obviously one of degree only and not of kind. The undulations of light may be compared to the thrust of a rapier, and the more massive waves of radiant heat to the blow of a bludgeon, but the same resistance which arrests the advance of the one must retard and finally arrest that of the other, if sufficiently extended. Within the limits of a space in which ProfessorStewart conceives that the first rays of light which ever flashed forth at the dawn of creation, in the primal æons of the universe, are still to this day, along their original lines of radiation, “traversing space at the rate of one hundred and eighty-eight thousand miles per second,” there must certainly be room enough and absorption enough (which even a few yards of mist will supply) to curb these runaway steeds somewhere along their lines of flaming passage. At that very point they are at work acting upon the molecules of the attenuated vapors of space, and assisting to re-establish the potential energy which has there been converted, into another form of force by the planetary rotations of the solar systems of those distant regions. By the law of the diffusion of gases, and that of the diffusion or transference of heat-energy from molecule to molecule, the vast realms of interstellar space must tend to be all brought into approximate uniformity of tensions, and the force abstracted at those points of space occupied by the relatively few and insignificant solar systems will be returned, not directly at the identical places where such solar systems may exist, but at every part of space to which their radiant energy extends. As we give from our own supplies to other systems for their support, so they, in turn, give back again to us. It is said that in the earliest days of creation the stars sang together; they still sing together, planets and suns, as“Jura answers from her misty shroudBack to the joyous Alps, who call to her aloud.”When old Earth lifts his brimming beaker from the great crystal sea and drains it to the good health of all the stars of heaven, they each respond with fiery energy, and by their merry twinkle we may know how highly they appreciate the toast. We are all one family,—but what a family! Comets, planets, double stars, variable stars, stars of complementary colors, blue, yellow, orange, and red stars, stars which blaze up in sudden conflagration, apparently new stars, nebulæ half star and half vapor, nebulæ all vapor and others all stars, the vast milky-way like a wondrous river of hundreds of millions of solar systems, the insulated stars scattered through space like watchmen on the distant hills beyond the city walls, streams of stars, stars which are parting from each other in space like scattering families, and those which travel together in groups like pioneers in a strange country,—all these and doubtless other unknown types and forms compose this sidereal family. Will they fall into their categories as lawful subjects, so as to be properly classified in a single scheme of the visible order of creation, or shall we fail to interpret their apparent mysteries when we apply the same principles which have been successfully applied to the phenomena of our own solar system? Let us see.In examining the sun, we find that a beam of its light passed through a prism is thrown upon the wall in a wedge-shaped streak of rainbow-tinted colors. Fraunhofer, many years ago, found that this spectrum was crossed at irregular intervalsby a series of dark lines, of variable width and distance apart, of which he catalogued more than five hundred. These lines were subsequently found to correspond in the aggregate, in their position in the spectrum, with a series of bright lines of different colors which formed the separate spectra of various metals when burned, in vapor or powder, in the flame of an alcohol lamp. Each of these transverse lines was found to have a fixed and invariable position in the extended scale of the spectrum, and scarcely any lines of the different elements are alike; so that, when the spectrum is properly magnified under telescopic observation and the lines identified, we have the means of determining the presence or absence of such elements in the vaporous constitution of any incandescent body by examination of its spectrum. In this way many of our terrestrial elements are found to exist in the sun,—so many, in fact, that we know that the sun’s nucleus, or core, must be composed substantially of the same elements, the same sort of matter, as exists on earth,—that we are, in fact, “a chip of the old block.” But it was found—and this is the real basis of spectrum analysis—that if a certain metal or other element be burned in the flame of an alcohol lamp, and a more brilliant flame of the same metal or element burned in another lamp be observed through the first flame, it will be seen that, “while the general illumination of the spectrum is increased, the previous bright lines characterizing the element are now replaced by dark lines or lines relatively veryfaint; in a word, the spectrum characteristic of the given element is exactly reversed” (Appleton’s Cyclopædia, article “Spectrum Analysis”). We have referred to this fact above in considering the origin of sun-spots, showing that they are due to increased heat acting upon the core of the sun so as to volatilize an abnormally large proportion of the elements usually in a more condensed state upon the surface of the solar body beneath its hydrogen envelope. These vapors, thus raised in temperature, are driven upward by their volatilization into the incandescent atmosphere of hydrogen, and the vaporous matters in the higher strata thus produce the characteristic absorption bands of these elements, while the overheatedvapors, by a vast uprush from beneath, hurl aside the more highly heated hydrogen above to appear as faculæ around the sun-spot, the cooler upper layers of hydrogen following downward the subsiding vaporous metallic uprush as it sinks back beneath the photospheric level.1 Solar.Dark HeatRedOrangeYellowGreenBlueVioletActinic2 Sodium,3 Calcium.4 Hydrogen (Absorption Spectrum)5 Hydrogen (Bright Line Spectrum)Spectra of different elements compared with the solar spectrum, and showing reversal of hydrogen lines under special circumstances.It is obvious that by similar spectrum analysis we may determine to a large extent the constitution of the fixed stars and other self-luminous bodies of space and interpret the phenomena which they exhibit. We quote the following from the previously cited article in Appleton’s Cyclopædia, by Professor Proctor: “Spectroscopic analysis applied to the stars has shown that they resemble the sun in general constitution and condition. But characteristic differences exist, insomuch that the stars have been divided into four orders distinguished by their spectra. These are thus presented by Secchi, who examined more than five hundred star spectra: The first type is represented by Alpha Lyræ, Sirius, etc., and includes most of the stars shining with a white light, as Altair, Regulus, Rigel, the stars Beta, Gamma, Epsilon, Zeta, and Eta of Ursa Major, etc. These give a spectrum showing all the seven colors, and crossed usually by many lines, butalways by the four lines of hydrogen, very dark and strong. The breadth of these four lines indicates a very deep, absorptive stratum at a high temperature and at great pressure.Nearly half the starsobserved by Secchi [more than two hundred out of five hundred] showed this spectrum. The second type includes most of theyellow stars, as Capella, Pollux, Arcturus, Aldebaran, Alpha of Ursa Major, Procyon, etc. The Fraunhofer lines are well seen in the red and blue, but not so well in the yellow.The resemblance of this spectrum to the sunsuggests that stars of this type resemble the sun closely in physical constitution and condition. About one-third of the stars observed by Secchi [more than one hundred and fifty out of five hundred] showed this spectrum. The third type includes Antares, Alpha of Orion, and Alpha of Hercules, Beta of Pegasus, Mira, and most of the stars shining with a red light. The spectra show bands of lines; according to Secchi, there are shaded bands, but a more powerful spectroscope shows multitudes of fine lines. The spectra resemble somewhat thespectrum of a sun-spot, and Secchi has advanced the theory that these stars are covered in great part by spots like those of the sun. About one hundred [out of five hundred] of the observed stars belong to this type.” (It should be noted that the presence of sun-spots is no evidence of diminished heat in a sun; see Professor Proctor in his “Myths and Marvels of Astronomy,” article “Suns in Flames:” “It may be noticed, in passing, that it is by no means certain that the time when the sun is most spotted is the time when he gives out least light …. All the evidence we have tends to show that when the sun is most spotted his energies are most active. It is then that the colored flames leap to their greatest height and show their greatest brilliancy, then also that they show the most rapid and remarkablechanges of shape.”) … “The fourth type differs from the preceding in the arrangement and appearance of the bands. It includes only faint stars. A few stars, as Gamma of Cassiopeia, Eta of Argus, Beta of Lyra, etc., show thelines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself around which the hydrogen exists.”Reversal and neutralization of spectroscopic lines in spectrum of a variable star like Betelgeuse.—1, photosphere hotter than chromosphere; hydrogen lines dark. 2, chromosphere hotter than photosphere; hydrogen lines bright. 3, chromosphere and photosphere equally incandescent.All the above five hundred stars reveal the presence of hydrogen under precisely such conditions as conform to the general principle involved in the source and mode of solar energy as herein stated. But a single star (Betelgeuse) was observed by Huggins and Miller in England which showed the lines of sodium, magnesium, iron, bismuth, and calcium, “but found those of hydrogen wanting.” Of the spectrum of this gas, Professor Ball says, “The hydrogen spectrum appears to present a simplicity not found in the spectrum of any other gas, and therefore it is with great interest that we examine the spectra of the white stars, in whichthe dark lines of hydrogenare unusually strong and broad.” Referring to the new star in the Northern Crown, which burst forth in 1866, the same writer says, “The feature which made the spectrum of the new star essentially distinct from that of any other star that had been previously observed was the presence ofcertain bright linessuperposed on a spectrum with dark lines of one of the ordinary types. The position of certain ofthese lines showed that one of the luminous gases must be hydrogen.” Ofthis particular star (Betelgeuse) it is said (Proctor’s “Familiar Essays”), “Red stars and variable stars affect the neighborhood of the Milky Way or of well-marked star-streams. The constellation Orion is singularly rich in objects of this class. It is here that the strange ‘variable’ Betelgeuse lies. At present this star shows no sign of variation, but a few years ago it exhibited remarkable changes.” We thus see that Betelgeuse is a variable star, and it must have passed in its different variations between the limits of extreme brilliancy, in which the lines of hydrogen appear bright, and that of a less brilliant stage, in which they appear dark,—that is, as absorption bands. It has thus, in fact, run the gamut, so to speak, of color changes, and now occupies an intermediate position in the scale. In his article “Star unto Star,” the same writer says, “On this view we may fairly assume that the darkness of the hydrogen lines is a characteristic of stars at a much higher temperature than our sun and suns of the same class.” We have already seen that the spectra of stars of the fourth type—Appleton’s Cyclopædia, “Spectrum Analysis”—“show the lines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself.” Professor Dunkin says, in his work “The Midnight Sky,” “One of the conclusions drawn by Kirchhoff from these experiments is that each incandescent gasweakens, by absorption, rays of the same degree of refrangibility as those it emits; or, in other words, that the spectrum of each incandescent gasis reversed when this gas is traversed by rays of the same refrangibility emanating from an intensely luminous source which gives of itself a continuous spectrum like that of the sun.” … “The third division, including Betelgeuse, Antares, Alpha Herculis, and others of like color, seems to be affected by something peculiar in their physical composition,as if their photospheres contained a quantity of gas at a lower temperature than usual. The stars in this class have generally a ruddy tint, probably owing to their light having undergone some modification while passing through an absorbing atmosphere …. A great number of the stars in the third division are variable in their lustre.” We may therefore readily conclude that midway between the inverted lines which constitute the dark absorption bands and the faint spectra which show the bright lines of hydrogen direct there must be an atmosphere of glowing hydrogen superposed upon a deeper one in such proportion that it willnot reveal its presence in the spectroscope at all; for when the dark and light bands, which occupy precisely the same position in the spectrum, are of approximately equal intensity the result will obviously be the neutralization of both. That among a myriad suns, some with dark hydrogen lines and some with bright, there should occur occasionally an example corresponding to this point of divergence, and especially among variable stars, is not only to be expected, but is, in fact, confirmatory of the general hypothesis itself. It is an exception which emphatically proves the rule, when we can trace the operative cause which has produced it.

CHAPTER V.THE DISTRIBUTION AND CONSERVATION OF SOLAR ENERGY.What, then, becomes of the light and heat flashed forth with eternal energy from the fiery waves of the sun’s incandescent atmosphere? Professor Ball (“In the High Heavens”) says, “Much of what has been said with regard to light may be repeated with regard to heat. We know that radiant heat consists of ethereal undulations of the same character as the waves of light. Hence we see that the heat or the light radiated from a glowing gas is mainly provided at the expense of the energy possessed by the molecules in virtue of their internal oscillations.” Conversely, of course, the ethereal undulations thus induced by high molecular motion in the heated gas or vapor must disappear in so-called absorption or transference by contact with other molecules, themselves devoid of such specific internal oscillations. The heat motion then disappears as heat by its conversion into work, just as the motion of a belt in a mill disappears in the work of the machine which it drives. One two-hundred-and-thirty-two-millionth part of the radiant solar energy, we know, is caught by the flying planets of our system in the forms of heat and light, adapted to sustain life and its continuedpotentiality, and we know that this solar energy is the sole source of all the development and maintenance of the planets as the possible abodes of organic life, past, present or future.But what of the vast total, of which we consume so minute a fraction? It is true that, in addition to the planets, space is occupied by many small meteoric bodies, which manifest themselves to us as shooting stars and meteorites, but the mass of these is too trifling to be estimated. Professor Helmholtz, in his “Popular Scientific Lectures,” says, “According to Alexander Herschel’s estimates, each stone is, on an average, at a distance of four hundred and fifty miles from its neighbors.” When these bodies enter our atmosphere by force of the earth’s attraction they are heated by its atmospheric friction to incandescence, and in most cases are even volatilized before reaching the earth’s surface. The vast volumes of solar heat and light, however, are poured forth from the sun indiscriminately in all directions into illimitable space, wherein all the masses of concrete matter, including the stars, are relatively far less in volume than the flying motes of the purest morning air which sparkle in the flood of light sent forth by the rising sun. Is all the rest wasted? Professor Balfour Stewart, in his work “The Conservation of Energy,” says, “If this be the fate of the high-temperature energy of the universe, let us think for a moment what will happen to its visible energy. We have spoken already about a medium pervading space, the office of which appears to be to degrade and ultimatelyextinguish all differential motion, just as it tends to reduce and ultimately equalize all difference in temperature. Thus, the universe would ultimately become an equally heated mass, utterly worthless as far as the production of work is concerned, since such production depends upon difference of temperature.”It is obvious that the starting-point taken by the author last quoted, but which, nevertheless, is in accordance with the views now generally prevalent, is diametrically opposed to that sought to be established in this work. Professor Stewart takes the sun’s inherent energy as the initial point of departure, and reasons from that as to the final consequence when all its light and heat shall have been distributed or dissipated into the attenuated medium which occupies space, and which will be thus slowly heated until all space has been raised in temperature to that of the last dying sun, when all will thenceforth remain unchanged and unchangeable, silent, dark, and dead, to all eternity. On the contrary, the purpose of the present work is to establish a directly opposite principle, based, however, on demonstrated scientific facts and not on theory, that the medium which pervades all space was originally in the same equally and universally potential state (with its molecules raised to a tension constituting an unstable equilibrium) in which, practically, Professor Stewart’s argument leaves it finally, and that this universal molecular energy of position was permanently maintained by the employment of the forces which afterwards,transformed into light and heat, were shed abroad by the sun in the work of again overcoming the intermolecular tension of cohesion, and that the light and heat of the sun are merely caught up again by these same or other molecules and successively employed in the same manner, while the planetary electrospheres utilize these same forces of internal tension in the generation of electricity, which, sent to the sun, is converted into light and heat, and these are again transferred to their original source. The rotation of the planets is the grand exciting cause, and the process, in its complete cycle of development, has live stages: first, planetary generation; second, transference by currents of electricity to the sun; third, conversion into light and heat; fourth, emission; and, fifth, reabsorption and conversion again into molecular energy of position. All space is thus found to be pervaded by extremely attenuated vapors, which contain the elemental constituents out of which suns and planets are evolved under favorable circumstances of development, and, among other vapors, aqueous vapor, and that these are the agency upon which the planetary electrospheres operate in their generation of electrical currents, and which vapors, in turn, by absorption of the solar energy of radiation, again transform this energy into mutually balanced electric potential, until it is once more disengaged as electricity by the rotating planetary electrospheres, and so on in a constant circuit forever repeated. It differs from perpetual motion, however, in that the planetary rotation is the externaland not the internal generative cause, since the electrical forces neither cause nor control these motions; they belong to the realm of gravity. The disassociation, moreover, is electrical and not chemical disassociation. The tensions are against cohesion and not against chemical affinity; are, in fact, similar to those which constitute our atmosphere a vast electrical reservoir; and the aqueous vapors, through all their changes, permanently remain as aqueous vapors, except those condensed portions disassociated by electrolytic action at the electrospheric poles, and which have no relation to the attenuated vapors of space, except in that the latter are their sources of supply. The process is analogous to what we see around us at all times in the atmosphere. While the process described by Professor Stewart resembles the emptying of the inherent water of a cloud, in the form of rain, into an ocean which never yields up its water again, so that, when the cloud has rained itself out, it is gone forever, the processes here sketched are like the vapors which are caught up by the heated air, carried over the thirsty lands, distributed in rain to fertilize and vivify them, then gathered in a thousand tiny rills from countless fountains, again descending to the sea and again carried up in vapor, and so on over and over in unceasing round. It is the difference between an old-fashioned flintlock musket and a modern magazine rifle, except that the magazine is always full.This great ocean of space was primordially charged with these potential vapors; it is theconstitution of space itself. We are so accustomed to consider space as empty, and that it is nothingness, the antithesis of something or anything, that it is a negation or a blank, that it requires an effort to even think of it as a fully stocked establishment with all the goods necessary for use or ornament, in the latest styles and of prime quality, only not made up, and that all our suns and worlds are merely tailoring establishments where the operatives cut and fit and make them up to order. When more goods are wanted they have to go to the store.Is space, then, eternal, and is this constant round of energies to be eternal? If one is eternal, so is the other, and surely nothing can be more eternal than space, and we cannot conceive of any other space than this space. Out of it came all created things, and so long as the orbs rotate without retardation, so long will these interchanges go on without impairment, and that they do so rotate is the necessary corollary of the fact that they ever began to rotate. If rotation, on the contrary, was imparted by special creative power, then the same power established the laws by which they rotate, and took cognizance of resistance as well. Whatever the impulse was, it still remains; whatever caused the rotation to begin maintains it; if the cause is eternal the rotation may be eternal; and, in any case, its period must be measured by cycles of æons, to which the allotted lifetime of a dying sun—a few million years, perhaps—is but as the sunburst of a morning-glory flower to the hoary age of a mighty planet. Compared with the popularview of the sun’s life-period, we may formulate the terms of an equation in which the sun’s mass, compared with the realms of infinite space, is as the sun’s lifetime—on a basis of contraction of his volume—to the lifetime which actually is to be. As one of the terms is practically infinite, so must be the answer to the problem. Professor Stewart says, “We cannot help believing that there is a material medium of some kind between the sun and the earth; indeed, the undulatory theory of light requires this belief.” It has already been shown that the transmission of electricity also requires it, but that there must be a medium quite different from the undulatory ether. Professor Proctor (“Mysteries of Time and Space”) says, “We may admit the possibility that the aqueous vapor and carbon compounds are present in stellar or interplanetary space.” Again he says, “Assuming, as we well may, that space is really occupied by attenuated vapors.” The same writer says further, “To this end all thoughtful study of the mechanism seems to tend (associating, perhaps, our visible universe with others, permeating it as the ether of space permeates the densest solids, and in turn with others so permeated by it); there may be that constant interchange, that perpetual harmony, of which Goethe sung:‘Balanced worlds from change defending,While everywhere diffused is harmony unending.’ ”The light and heat poured forth from the sun are, as stated, in the form of radiated energy.They penetrate the attenuated vapors as far as vision extends, and doubtless farther, but they cannot reach the boundaries of space, for even the mind of man cannot reach those limits. Aqueous vapor absorbs heat; we know this without any demonstration, for the radiated heat of the earth is arrested by a veil of clouds, so that on cloudy nights frost will not form. So also the sun shining into water will raise its temperature, as in a glass globe, and such absorption of heat by aqueous vapors or water would be much more manifest were not a large part employed in loosening the tension of the constituent molecules, since, when thus employed, it is not manifest as sensible heat. Professor Tyndall, in “The Forms of Water,” states that “The quantity of heat which would raise the temperature of a pound of water one degree would raise the temperature of a pound of iron ten degrees.” Professor Stewart, in “The Conservation of Energy,” says, “That peculiar motion which is imparted by heat when absorbed into a body is, therefore, one variety of molecular energy …. Part of the energy of absorbed heat is spent in pulling asunder the molecules of the body under the attractive force which binds them together, and thus a store ofenergy of positionis laid up, which disappears again after the body is cooled.“Heat will only be changed into work while it passes from a body of high temperature to one of low …. At very high temperatures it is possible that most compounds are decomposed, and thetemperature at which this takes place, for any compound, has been termed its temperature of disassociation.Heat energy is changed into electrical separationwhen tourmalines and certain other crystals are heated.” It may be added that it is also changed into electrical energy by the operation of all electrical machines, as molecular motions are all mutually interconvertible, and heat itself is only a mode of such motion. Of radiant energy, the same writer says, “This form of energy [radiant heat] is converted into absorbed heat whenever it falls upon an opaque substance … and heats it. It is a curious question to ask what becomes of theradiant lightfrom the sun that is not absorbed either by the planets of our system or by any of the stars. We can only reply to such a question that,as far as we can judge from our present knowledge, the radiant energy that is not absorbed must be conceived to be traversing space at the rate of one hundred and eighty-eight thousand miles a second.”We know, of course, that aqueous vapors are partially opaque to heat rays, as the radiated heat of the earth is partially arrested by such vapors in the atmosphere, but they are apparently transparent to the rays of light. But we know that this cannot be entirely true in fact, for light rays only differ from heat rays in the comparative length of their waves or impulses, while rays of light are always accompanied—when emitted by a thermally incandescent body—by a much larger number of those of heat. As a body is raised in temperature radiant dark rays first appear; these being raised higher, becomevisible as light, and new dark rays are radiated behind them, and this continues till after the state of highest incandescence is reached and the invisible chemical rays beyond the spectrum appear. It is like a crowd surging forth in flight from the doors of a building; as the speed of those in front increases to a run, others follow more slowly in the mass, and as these gain speed others continue to follow, while the great mass of laggards still trails along in a lengthening line to the rear. The perception of light is itself merely due to the constitution of the optic apparatus of the observer, which only takes cognizance of vibrations radiated from the middle portion of the scale, just as the ear does with sounds, and not to any actual difference in their mode of production. That heat rays and light rays are identical in constitution can be readily shown by the experiment described by Professor Tyndall in his “Forms of Water,” in which an opaque screen of iodine solution in bisulphide of carbon was employed to arrest, in a beam of light, all the light waves (to which it is entirely opaque), while transmitting the dark rays. These non-luminous rays are then converged by a lens: “Let us, then, by means of our opaque solution, isolate our dark waves and converge them on the cotton. It explodes as before …. At the same dark focus sheets of platinum are raised to vivid redness; … a diamond is caused to glow like a star, being afterwards gradually dissipated.” Sir William Herschel (see article “Spectrum,” Appleton’s Cyclopædia) says, “If we call light those rays which illuminateobjects, and radiant heat those which heat bodies, it may be inquired whether light be essentially different from radiant heat. In answer to which I would suggest that we are not allowed by the rules of philosophizing to admit of two different causes to explain certain effects, if they may be accounted for by one.”… “Tyndall, by similar experiments, found that the thermal energy of the invisible radiation of a very powerful electric light is eight times that of the visible …. Seebeck showed that the position of maximum heat in the spectrum changes with the nature of the prism and sometimes occurs in the red.” Melconi, with prisms of alcohol and water, found it in the yellow. Athermic bands are also found in the heat-spectrum, corresponding to the Fraunhofer lines seen in the visible spectrum.We may illustrate this successive development of more and more rapid light-waves by conceiving of a harp having musical strings of various length and thickness, but not strung up, so that, when swept by the hand, the vibrations are felt, but no musical tones are produced. If, now, all the strings are simultaneously and gradually stretched while under continuous vibration, we will first hear the hum of the lighter strings, but deep down in the scale; and as the tension gradually increases the pitch of these will rise higher and higher and be succeeded by other new tones below, until the whole register is simultaneously sounded. And if the tension be further increased, the vibrations of the upper strings will gradually grow so rapid that the ear can take no cognizance of them, correspondingto the invisible chemical rays of the spectrum, while the middle strings will be sounding loudly, and others will be slowly vibrating below the musical scale, but without sound, corresponding to the invisible heat rays. In addition to this gradual ascent of pitch along the scale, however, there is reason to believe that sympathetic vibrations are induced in the spectrum of thermal and chemical light corresponding to the over-tones in music and to those hidden rhythms which differentiate the “timbre” of one kind of musical instrument from that of another, so that a definite wave-length will not only repeat itself among adjacent molecules, but will give rise to harmonious vibrations quite different in amplitude and velocity. An example of this is found in some of the phenomena of phosphorescence and fluorescence, in which chemical rays totally invisible are able, under suitable conditions, to excite molecular movements corresponding to parts of the visible spectrum, and quite different in wave-lengths and in rapidity. This process is precisely the converse of what we perceive in thermal light; in the latter case the colors ascend, loaded with invisible heat rays; in the former they descend, loaded with invisible chemical rays, only noted, perhaps, by their actinic action on the photographic plate. Others, as the sulphide of calcium paints and the like, repeat their own vibrations for many hours, and we find in certain chemical salts of some rare metals, as lanthanum and cerium, the curious property of suddenly raising the whole scale, as in a recently introducedgas-lamp, in which a skeleton mantle of these oxides glows with a wondrously beautiful white light under the relatively low temperature of a small Bunsen burner; similar phenomena are manifested in the behavior of electric discharges in attenuated gases, as well as in what is known to children as “fox-fire,” wood undergoing slow decomposition in damp places, or in the self-luminous secretions (corresponding, perhaps, to ptomaines or like products) of glow-worms and other animals. If we ever—as we probably soon shall—reach that point where we can illuminate our dwellings with “cold candles,” as the inhabitants of tropical countries carry about a few fire-flies in a paper box for a lantern on dark nights, it must be by the study of these phenomena. But meantime “Old Sol” will continue to discharge his accumulating stores of both heat and light, for both these are essential, not only for use upon the planets, but throughout all the realms of space. In the transformation into and emission of his radiant energy the sun is not a chemical engine, but a mill,—one of those which “grind slowly, but they grind exceeding small.”The difference between radiated thermal light and heat is obviously one of degree only and not of kind. The undulations of light may be compared to the thrust of a rapier, and the more massive waves of radiant heat to the blow of a bludgeon, but the same resistance which arrests the advance of the one must retard and finally arrest that of the other, if sufficiently extended. Within the limits of a space in which ProfessorStewart conceives that the first rays of light which ever flashed forth at the dawn of creation, in the primal æons of the universe, are still to this day, along their original lines of radiation, “traversing space at the rate of one hundred and eighty-eight thousand miles per second,” there must certainly be room enough and absorption enough (which even a few yards of mist will supply) to curb these runaway steeds somewhere along their lines of flaming passage. At that very point they are at work acting upon the molecules of the attenuated vapors of space, and assisting to re-establish the potential energy which has there been converted, into another form of force by the planetary rotations of the solar systems of those distant regions. By the law of the diffusion of gases, and that of the diffusion or transference of heat-energy from molecule to molecule, the vast realms of interstellar space must tend to be all brought into approximate uniformity of tensions, and the force abstracted at those points of space occupied by the relatively few and insignificant solar systems will be returned, not directly at the identical places where such solar systems may exist, but at every part of space to which their radiant energy extends. As we give from our own supplies to other systems for their support, so they, in turn, give back again to us. It is said that in the earliest days of creation the stars sang together; they still sing together, planets and suns, as“Jura answers from her misty shroudBack to the joyous Alps, who call to her aloud.”When old Earth lifts his brimming beaker from the great crystal sea and drains it to the good health of all the stars of heaven, they each respond with fiery energy, and by their merry twinkle we may know how highly they appreciate the toast. We are all one family,—but what a family! Comets, planets, double stars, variable stars, stars of complementary colors, blue, yellow, orange, and red stars, stars which blaze up in sudden conflagration, apparently new stars, nebulæ half star and half vapor, nebulæ all vapor and others all stars, the vast milky-way like a wondrous river of hundreds of millions of solar systems, the insulated stars scattered through space like watchmen on the distant hills beyond the city walls, streams of stars, stars which are parting from each other in space like scattering families, and those which travel together in groups like pioneers in a strange country,—all these and doubtless other unknown types and forms compose this sidereal family. Will they fall into their categories as lawful subjects, so as to be properly classified in a single scheme of the visible order of creation, or shall we fail to interpret their apparent mysteries when we apply the same principles which have been successfully applied to the phenomena of our own solar system? Let us see.In examining the sun, we find that a beam of its light passed through a prism is thrown upon the wall in a wedge-shaped streak of rainbow-tinted colors. Fraunhofer, many years ago, found that this spectrum was crossed at irregular intervalsby a series of dark lines, of variable width and distance apart, of which he catalogued more than five hundred. These lines were subsequently found to correspond in the aggregate, in their position in the spectrum, with a series of bright lines of different colors which formed the separate spectra of various metals when burned, in vapor or powder, in the flame of an alcohol lamp. Each of these transverse lines was found to have a fixed and invariable position in the extended scale of the spectrum, and scarcely any lines of the different elements are alike; so that, when the spectrum is properly magnified under telescopic observation and the lines identified, we have the means of determining the presence or absence of such elements in the vaporous constitution of any incandescent body by examination of its spectrum. In this way many of our terrestrial elements are found to exist in the sun,—so many, in fact, that we know that the sun’s nucleus, or core, must be composed substantially of the same elements, the same sort of matter, as exists on earth,—that we are, in fact, “a chip of the old block.” But it was found—and this is the real basis of spectrum analysis—that if a certain metal or other element be burned in the flame of an alcohol lamp, and a more brilliant flame of the same metal or element burned in another lamp be observed through the first flame, it will be seen that, “while the general illumination of the spectrum is increased, the previous bright lines characterizing the element are now replaced by dark lines or lines relatively veryfaint; in a word, the spectrum characteristic of the given element is exactly reversed” (Appleton’s Cyclopædia, article “Spectrum Analysis”). We have referred to this fact above in considering the origin of sun-spots, showing that they are due to increased heat acting upon the core of the sun so as to volatilize an abnormally large proportion of the elements usually in a more condensed state upon the surface of the solar body beneath its hydrogen envelope. These vapors, thus raised in temperature, are driven upward by their volatilization into the incandescent atmosphere of hydrogen, and the vaporous matters in the higher strata thus produce the characteristic absorption bands of these elements, while the overheatedvapors, by a vast uprush from beneath, hurl aside the more highly heated hydrogen above to appear as faculæ around the sun-spot, the cooler upper layers of hydrogen following downward the subsiding vaporous metallic uprush as it sinks back beneath the photospheric level.1 Solar.Dark HeatRedOrangeYellowGreenBlueVioletActinic2 Sodium,3 Calcium.4 Hydrogen (Absorption Spectrum)5 Hydrogen (Bright Line Spectrum)Spectra of different elements compared with the solar spectrum, and showing reversal of hydrogen lines under special circumstances.It is obvious that by similar spectrum analysis we may determine to a large extent the constitution of the fixed stars and other self-luminous bodies of space and interpret the phenomena which they exhibit. We quote the following from the previously cited article in Appleton’s Cyclopædia, by Professor Proctor: “Spectroscopic analysis applied to the stars has shown that they resemble the sun in general constitution and condition. But characteristic differences exist, insomuch that the stars have been divided into four orders distinguished by their spectra. These are thus presented by Secchi, who examined more than five hundred star spectra: The first type is represented by Alpha Lyræ, Sirius, etc., and includes most of the stars shining with a white light, as Altair, Regulus, Rigel, the stars Beta, Gamma, Epsilon, Zeta, and Eta of Ursa Major, etc. These give a spectrum showing all the seven colors, and crossed usually by many lines, butalways by the four lines of hydrogen, very dark and strong. The breadth of these four lines indicates a very deep, absorptive stratum at a high temperature and at great pressure.Nearly half the starsobserved by Secchi [more than two hundred out of five hundred] showed this spectrum. The second type includes most of theyellow stars, as Capella, Pollux, Arcturus, Aldebaran, Alpha of Ursa Major, Procyon, etc. The Fraunhofer lines are well seen in the red and blue, but not so well in the yellow.The resemblance of this spectrum to the sunsuggests that stars of this type resemble the sun closely in physical constitution and condition. About one-third of the stars observed by Secchi [more than one hundred and fifty out of five hundred] showed this spectrum. The third type includes Antares, Alpha of Orion, and Alpha of Hercules, Beta of Pegasus, Mira, and most of the stars shining with a red light. The spectra show bands of lines; according to Secchi, there are shaded bands, but a more powerful spectroscope shows multitudes of fine lines. The spectra resemble somewhat thespectrum of a sun-spot, and Secchi has advanced the theory that these stars are covered in great part by spots like those of the sun. About one hundred [out of five hundred] of the observed stars belong to this type.” (It should be noted that the presence of sun-spots is no evidence of diminished heat in a sun; see Professor Proctor in his “Myths and Marvels of Astronomy,” article “Suns in Flames:” “It may be noticed, in passing, that it is by no means certain that the time when the sun is most spotted is the time when he gives out least light …. All the evidence we have tends to show that when the sun is most spotted his energies are most active. It is then that the colored flames leap to their greatest height and show their greatest brilliancy, then also that they show the most rapid and remarkablechanges of shape.”) … “The fourth type differs from the preceding in the arrangement and appearance of the bands. It includes only faint stars. A few stars, as Gamma of Cassiopeia, Eta of Argus, Beta of Lyra, etc., show thelines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself around which the hydrogen exists.”Reversal and neutralization of spectroscopic lines in spectrum of a variable star like Betelgeuse.—1, photosphere hotter than chromosphere; hydrogen lines dark. 2, chromosphere hotter than photosphere; hydrogen lines bright. 3, chromosphere and photosphere equally incandescent.All the above five hundred stars reveal the presence of hydrogen under precisely such conditions as conform to the general principle involved in the source and mode of solar energy as herein stated. But a single star (Betelgeuse) was observed by Huggins and Miller in England which showed the lines of sodium, magnesium, iron, bismuth, and calcium, “but found those of hydrogen wanting.” Of the spectrum of this gas, Professor Ball says, “The hydrogen spectrum appears to present a simplicity not found in the spectrum of any other gas, and therefore it is with great interest that we examine the spectra of the white stars, in whichthe dark lines of hydrogenare unusually strong and broad.” Referring to the new star in the Northern Crown, which burst forth in 1866, the same writer says, “The feature which made the spectrum of the new star essentially distinct from that of any other star that had been previously observed was the presence ofcertain bright linessuperposed on a spectrum with dark lines of one of the ordinary types. The position of certain ofthese lines showed that one of the luminous gases must be hydrogen.” Ofthis particular star (Betelgeuse) it is said (Proctor’s “Familiar Essays”), “Red stars and variable stars affect the neighborhood of the Milky Way or of well-marked star-streams. The constellation Orion is singularly rich in objects of this class. It is here that the strange ‘variable’ Betelgeuse lies. At present this star shows no sign of variation, but a few years ago it exhibited remarkable changes.” We thus see that Betelgeuse is a variable star, and it must have passed in its different variations between the limits of extreme brilliancy, in which the lines of hydrogen appear bright, and that of a less brilliant stage, in which they appear dark,—that is, as absorption bands. It has thus, in fact, run the gamut, so to speak, of color changes, and now occupies an intermediate position in the scale. In his article “Star unto Star,” the same writer says, “On this view we may fairly assume that the darkness of the hydrogen lines is a characteristic of stars at a much higher temperature than our sun and suns of the same class.” We have already seen that the spectra of stars of the fourth type—Appleton’s Cyclopædia, “Spectrum Analysis”—“show the lines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself.” Professor Dunkin says, in his work “The Midnight Sky,” “One of the conclusions drawn by Kirchhoff from these experiments is that each incandescent gasweakens, by absorption, rays of the same degree of refrangibility as those it emits; or, in other words, that the spectrum of each incandescent gasis reversed when this gas is traversed by rays of the same refrangibility emanating from an intensely luminous source which gives of itself a continuous spectrum like that of the sun.” … “The third division, including Betelgeuse, Antares, Alpha Herculis, and others of like color, seems to be affected by something peculiar in their physical composition,as if their photospheres contained a quantity of gas at a lower temperature than usual. The stars in this class have generally a ruddy tint, probably owing to their light having undergone some modification while passing through an absorbing atmosphere …. A great number of the stars in the third division are variable in their lustre.” We may therefore readily conclude that midway between the inverted lines which constitute the dark absorption bands and the faint spectra which show the bright lines of hydrogen direct there must be an atmosphere of glowing hydrogen superposed upon a deeper one in such proportion that it willnot reveal its presence in the spectroscope at all; for when the dark and light bands, which occupy precisely the same position in the spectrum, are of approximately equal intensity the result will obviously be the neutralization of both. That among a myriad suns, some with dark hydrogen lines and some with bright, there should occur occasionally an example corresponding to this point of divergence, and especially among variable stars, is not only to be expected, but is, in fact, confirmatory of the general hypothesis itself. It is an exception which emphatically proves the rule, when we can trace the operative cause which has produced it.

CHAPTER V.THE DISTRIBUTION AND CONSERVATION OF SOLAR ENERGY.

What, then, becomes of the light and heat flashed forth with eternal energy from the fiery waves of the sun’s incandescent atmosphere? Professor Ball (“In the High Heavens”) says, “Much of what has been said with regard to light may be repeated with regard to heat. We know that radiant heat consists of ethereal undulations of the same character as the waves of light. Hence we see that the heat or the light radiated from a glowing gas is mainly provided at the expense of the energy possessed by the molecules in virtue of their internal oscillations.” Conversely, of course, the ethereal undulations thus induced by high molecular motion in the heated gas or vapor must disappear in so-called absorption or transference by contact with other molecules, themselves devoid of such specific internal oscillations. The heat motion then disappears as heat by its conversion into work, just as the motion of a belt in a mill disappears in the work of the machine which it drives. One two-hundred-and-thirty-two-millionth part of the radiant solar energy, we know, is caught by the flying planets of our system in the forms of heat and light, adapted to sustain life and its continuedpotentiality, and we know that this solar energy is the sole source of all the development and maintenance of the planets as the possible abodes of organic life, past, present or future.But what of the vast total, of which we consume so minute a fraction? It is true that, in addition to the planets, space is occupied by many small meteoric bodies, which manifest themselves to us as shooting stars and meteorites, but the mass of these is too trifling to be estimated. Professor Helmholtz, in his “Popular Scientific Lectures,” says, “According to Alexander Herschel’s estimates, each stone is, on an average, at a distance of four hundred and fifty miles from its neighbors.” When these bodies enter our atmosphere by force of the earth’s attraction they are heated by its atmospheric friction to incandescence, and in most cases are even volatilized before reaching the earth’s surface. The vast volumes of solar heat and light, however, are poured forth from the sun indiscriminately in all directions into illimitable space, wherein all the masses of concrete matter, including the stars, are relatively far less in volume than the flying motes of the purest morning air which sparkle in the flood of light sent forth by the rising sun. Is all the rest wasted? Professor Balfour Stewart, in his work “The Conservation of Energy,” says, “If this be the fate of the high-temperature energy of the universe, let us think for a moment what will happen to its visible energy. We have spoken already about a medium pervading space, the office of which appears to be to degrade and ultimatelyextinguish all differential motion, just as it tends to reduce and ultimately equalize all difference in temperature. Thus, the universe would ultimately become an equally heated mass, utterly worthless as far as the production of work is concerned, since such production depends upon difference of temperature.”It is obvious that the starting-point taken by the author last quoted, but which, nevertheless, is in accordance with the views now generally prevalent, is diametrically opposed to that sought to be established in this work. Professor Stewart takes the sun’s inherent energy as the initial point of departure, and reasons from that as to the final consequence when all its light and heat shall have been distributed or dissipated into the attenuated medium which occupies space, and which will be thus slowly heated until all space has been raised in temperature to that of the last dying sun, when all will thenceforth remain unchanged and unchangeable, silent, dark, and dead, to all eternity. On the contrary, the purpose of the present work is to establish a directly opposite principle, based, however, on demonstrated scientific facts and not on theory, that the medium which pervades all space was originally in the same equally and universally potential state (with its molecules raised to a tension constituting an unstable equilibrium) in which, practically, Professor Stewart’s argument leaves it finally, and that this universal molecular energy of position was permanently maintained by the employment of the forces which afterwards,transformed into light and heat, were shed abroad by the sun in the work of again overcoming the intermolecular tension of cohesion, and that the light and heat of the sun are merely caught up again by these same or other molecules and successively employed in the same manner, while the planetary electrospheres utilize these same forces of internal tension in the generation of electricity, which, sent to the sun, is converted into light and heat, and these are again transferred to their original source. The rotation of the planets is the grand exciting cause, and the process, in its complete cycle of development, has live stages: first, planetary generation; second, transference by currents of electricity to the sun; third, conversion into light and heat; fourth, emission; and, fifth, reabsorption and conversion again into molecular energy of position. All space is thus found to be pervaded by extremely attenuated vapors, which contain the elemental constituents out of which suns and planets are evolved under favorable circumstances of development, and, among other vapors, aqueous vapor, and that these are the agency upon which the planetary electrospheres operate in their generation of electrical currents, and which vapors, in turn, by absorption of the solar energy of radiation, again transform this energy into mutually balanced electric potential, until it is once more disengaged as electricity by the rotating planetary electrospheres, and so on in a constant circuit forever repeated. It differs from perpetual motion, however, in that the planetary rotation is the externaland not the internal generative cause, since the electrical forces neither cause nor control these motions; they belong to the realm of gravity. The disassociation, moreover, is electrical and not chemical disassociation. The tensions are against cohesion and not against chemical affinity; are, in fact, similar to those which constitute our atmosphere a vast electrical reservoir; and the aqueous vapors, through all their changes, permanently remain as aqueous vapors, except those condensed portions disassociated by electrolytic action at the electrospheric poles, and which have no relation to the attenuated vapors of space, except in that the latter are their sources of supply. The process is analogous to what we see around us at all times in the atmosphere. While the process described by Professor Stewart resembles the emptying of the inherent water of a cloud, in the form of rain, into an ocean which never yields up its water again, so that, when the cloud has rained itself out, it is gone forever, the processes here sketched are like the vapors which are caught up by the heated air, carried over the thirsty lands, distributed in rain to fertilize and vivify them, then gathered in a thousand tiny rills from countless fountains, again descending to the sea and again carried up in vapor, and so on over and over in unceasing round. It is the difference between an old-fashioned flintlock musket and a modern magazine rifle, except that the magazine is always full.This great ocean of space was primordially charged with these potential vapors; it is theconstitution of space itself. We are so accustomed to consider space as empty, and that it is nothingness, the antithesis of something or anything, that it is a negation or a blank, that it requires an effort to even think of it as a fully stocked establishment with all the goods necessary for use or ornament, in the latest styles and of prime quality, only not made up, and that all our suns and worlds are merely tailoring establishments where the operatives cut and fit and make them up to order. When more goods are wanted they have to go to the store.Is space, then, eternal, and is this constant round of energies to be eternal? If one is eternal, so is the other, and surely nothing can be more eternal than space, and we cannot conceive of any other space than this space. Out of it came all created things, and so long as the orbs rotate without retardation, so long will these interchanges go on without impairment, and that they do so rotate is the necessary corollary of the fact that they ever began to rotate. If rotation, on the contrary, was imparted by special creative power, then the same power established the laws by which they rotate, and took cognizance of resistance as well. Whatever the impulse was, it still remains; whatever caused the rotation to begin maintains it; if the cause is eternal the rotation may be eternal; and, in any case, its period must be measured by cycles of æons, to which the allotted lifetime of a dying sun—a few million years, perhaps—is but as the sunburst of a morning-glory flower to the hoary age of a mighty planet. Compared with the popularview of the sun’s life-period, we may formulate the terms of an equation in which the sun’s mass, compared with the realms of infinite space, is as the sun’s lifetime—on a basis of contraction of his volume—to the lifetime which actually is to be. As one of the terms is practically infinite, so must be the answer to the problem. Professor Stewart says, “We cannot help believing that there is a material medium of some kind between the sun and the earth; indeed, the undulatory theory of light requires this belief.” It has already been shown that the transmission of electricity also requires it, but that there must be a medium quite different from the undulatory ether. Professor Proctor (“Mysteries of Time and Space”) says, “We may admit the possibility that the aqueous vapor and carbon compounds are present in stellar or interplanetary space.” Again he says, “Assuming, as we well may, that space is really occupied by attenuated vapors.” The same writer says further, “To this end all thoughtful study of the mechanism seems to tend (associating, perhaps, our visible universe with others, permeating it as the ether of space permeates the densest solids, and in turn with others so permeated by it); there may be that constant interchange, that perpetual harmony, of which Goethe sung:‘Balanced worlds from change defending,While everywhere diffused is harmony unending.’ ”The light and heat poured forth from the sun are, as stated, in the form of radiated energy.They penetrate the attenuated vapors as far as vision extends, and doubtless farther, but they cannot reach the boundaries of space, for even the mind of man cannot reach those limits. Aqueous vapor absorbs heat; we know this without any demonstration, for the radiated heat of the earth is arrested by a veil of clouds, so that on cloudy nights frost will not form. So also the sun shining into water will raise its temperature, as in a glass globe, and such absorption of heat by aqueous vapors or water would be much more manifest were not a large part employed in loosening the tension of the constituent molecules, since, when thus employed, it is not manifest as sensible heat. Professor Tyndall, in “The Forms of Water,” states that “The quantity of heat which would raise the temperature of a pound of water one degree would raise the temperature of a pound of iron ten degrees.” Professor Stewart, in “The Conservation of Energy,” says, “That peculiar motion which is imparted by heat when absorbed into a body is, therefore, one variety of molecular energy …. Part of the energy of absorbed heat is spent in pulling asunder the molecules of the body under the attractive force which binds them together, and thus a store ofenergy of positionis laid up, which disappears again after the body is cooled.“Heat will only be changed into work while it passes from a body of high temperature to one of low …. At very high temperatures it is possible that most compounds are decomposed, and thetemperature at which this takes place, for any compound, has been termed its temperature of disassociation.Heat energy is changed into electrical separationwhen tourmalines and certain other crystals are heated.” It may be added that it is also changed into electrical energy by the operation of all electrical machines, as molecular motions are all mutually interconvertible, and heat itself is only a mode of such motion. Of radiant energy, the same writer says, “This form of energy [radiant heat] is converted into absorbed heat whenever it falls upon an opaque substance … and heats it. It is a curious question to ask what becomes of theradiant lightfrom the sun that is not absorbed either by the planets of our system or by any of the stars. We can only reply to such a question that,as far as we can judge from our present knowledge, the radiant energy that is not absorbed must be conceived to be traversing space at the rate of one hundred and eighty-eight thousand miles a second.”We know, of course, that aqueous vapors are partially opaque to heat rays, as the radiated heat of the earth is partially arrested by such vapors in the atmosphere, but they are apparently transparent to the rays of light. But we know that this cannot be entirely true in fact, for light rays only differ from heat rays in the comparative length of their waves or impulses, while rays of light are always accompanied—when emitted by a thermally incandescent body—by a much larger number of those of heat. As a body is raised in temperature radiant dark rays first appear; these being raised higher, becomevisible as light, and new dark rays are radiated behind them, and this continues till after the state of highest incandescence is reached and the invisible chemical rays beyond the spectrum appear. It is like a crowd surging forth in flight from the doors of a building; as the speed of those in front increases to a run, others follow more slowly in the mass, and as these gain speed others continue to follow, while the great mass of laggards still trails along in a lengthening line to the rear. The perception of light is itself merely due to the constitution of the optic apparatus of the observer, which only takes cognizance of vibrations radiated from the middle portion of the scale, just as the ear does with sounds, and not to any actual difference in their mode of production. That heat rays and light rays are identical in constitution can be readily shown by the experiment described by Professor Tyndall in his “Forms of Water,” in which an opaque screen of iodine solution in bisulphide of carbon was employed to arrest, in a beam of light, all the light waves (to which it is entirely opaque), while transmitting the dark rays. These non-luminous rays are then converged by a lens: “Let us, then, by means of our opaque solution, isolate our dark waves and converge them on the cotton. It explodes as before …. At the same dark focus sheets of platinum are raised to vivid redness; … a diamond is caused to glow like a star, being afterwards gradually dissipated.” Sir William Herschel (see article “Spectrum,” Appleton’s Cyclopædia) says, “If we call light those rays which illuminateobjects, and radiant heat those which heat bodies, it may be inquired whether light be essentially different from radiant heat. In answer to which I would suggest that we are not allowed by the rules of philosophizing to admit of two different causes to explain certain effects, if they may be accounted for by one.”… “Tyndall, by similar experiments, found that the thermal energy of the invisible radiation of a very powerful electric light is eight times that of the visible …. Seebeck showed that the position of maximum heat in the spectrum changes with the nature of the prism and sometimes occurs in the red.” Melconi, with prisms of alcohol and water, found it in the yellow. Athermic bands are also found in the heat-spectrum, corresponding to the Fraunhofer lines seen in the visible spectrum.We may illustrate this successive development of more and more rapid light-waves by conceiving of a harp having musical strings of various length and thickness, but not strung up, so that, when swept by the hand, the vibrations are felt, but no musical tones are produced. If, now, all the strings are simultaneously and gradually stretched while under continuous vibration, we will first hear the hum of the lighter strings, but deep down in the scale; and as the tension gradually increases the pitch of these will rise higher and higher and be succeeded by other new tones below, until the whole register is simultaneously sounded. And if the tension be further increased, the vibrations of the upper strings will gradually grow so rapid that the ear can take no cognizance of them, correspondingto the invisible chemical rays of the spectrum, while the middle strings will be sounding loudly, and others will be slowly vibrating below the musical scale, but without sound, corresponding to the invisible heat rays. In addition to this gradual ascent of pitch along the scale, however, there is reason to believe that sympathetic vibrations are induced in the spectrum of thermal and chemical light corresponding to the over-tones in music and to those hidden rhythms which differentiate the “timbre” of one kind of musical instrument from that of another, so that a definite wave-length will not only repeat itself among adjacent molecules, but will give rise to harmonious vibrations quite different in amplitude and velocity. An example of this is found in some of the phenomena of phosphorescence and fluorescence, in which chemical rays totally invisible are able, under suitable conditions, to excite molecular movements corresponding to parts of the visible spectrum, and quite different in wave-lengths and in rapidity. This process is precisely the converse of what we perceive in thermal light; in the latter case the colors ascend, loaded with invisible heat rays; in the former they descend, loaded with invisible chemical rays, only noted, perhaps, by their actinic action on the photographic plate. Others, as the sulphide of calcium paints and the like, repeat their own vibrations for many hours, and we find in certain chemical salts of some rare metals, as lanthanum and cerium, the curious property of suddenly raising the whole scale, as in a recently introducedgas-lamp, in which a skeleton mantle of these oxides glows with a wondrously beautiful white light under the relatively low temperature of a small Bunsen burner; similar phenomena are manifested in the behavior of electric discharges in attenuated gases, as well as in what is known to children as “fox-fire,” wood undergoing slow decomposition in damp places, or in the self-luminous secretions (corresponding, perhaps, to ptomaines or like products) of glow-worms and other animals. If we ever—as we probably soon shall—reach that point where we can illuminate our dwellings with “cold candles,” as the inhabitants of tropical countries carry about a few fire-flies in a paper box for a lantern on dark nights, it must be by the study of these phenomena. But meantime “Old Sol” will continue to discharge his accumulating stores of both heat and light, for both these are essential, not only for use upon the planets, but throughout all the realms of space. In the transformation into and emission of his radiant energy the sun is not a chemical engine, but a mill,—one of those which “grind slowly, but they grind exceeding small.”The difference between radiated thermal light and heat is obviously one of degree only and not of kind. The undulations of light may be compared to the thrust of a rapier, and the more massive waves of radiant heat to the blow of a bludgeon, but the same resistance which arrests the advance of the one must retard and finally arrest that of the other, if sufficiently extended. Within the limits of a space in which ProfessorStewart conceives that the first rays of light which ever flashed forth at the dawn of creation, in the primal æons of the universe, are still to this day, along their original lines of radiation, “traversing space at the rate of one hundred and eighty-eight thousand miles per second,” there must certainly be room enough and absorption enough (which even a few yards of mist will supply) to curb these runaway steeds somewhere along their lines of flaming passage. At that very point they are at work acting upon the molecules of the attenuated vapors of space, and assisting to re-establish the potential energy which has there been converted, into another form of force by the planetary rotations of the solar systems of those distant regions. By the law of the diffusion of gases, and that of the diffusion or transference of heat-energy from molecule to molecule, the vast realms of interstellar space must tend to be all brought into approximate uniformity of tensions, and the force abstracted at those points of space occupied by the relatively few and insignificant solar systems will be returned, not directly at the identical places where such solar systems may exist, but at every part of space to which their radiant energy extends. As we give from our own supplies to other systems for their support, so they, in turn, give back again to us. It is said that in the earliest days of creation the stars sang together; they still sing together, planets and suns, as“Jura answers from her misty shroudBack to the joyous Alps, who call to her aloud.”When old Earth lifts his brimming beaker from the great crystal sea and drains it to the good health of all the stars of heaven, they each respond with fiery energy, and by their merry twinkle we may know how highly they appreciate the toast. We are all one family,—but what a family! Comets, planets, double stars, variable stars, stars of complementary colors, blue, yellow, orange, and red stars, stars which blaze up in sudden conflagration, apparently new stars, nebulæ half star and half vapor, nebulæ all vapor and others all stars, the vast milky-way like a wondrous river of hundreds of millions of solar systems, the insulated stars scattered through space like watchmen on the distant hills beyond the city walls, streams of stars, stars which are parting from each other in space like scattering families, and those which travel together in groups like pioneers in a strange country,—all these and doubtless other unknown types and forms compose this sidereal family. Will they fall into their categories as lawful subjects, so as to be properly classified in a single scheme of the visible order of creation, or shall we fail to interpret their apparent mysteries when we apply the same principles which have been successfully applied to the phenomena of our own solar system? Let us see.In examining the sun, we find that a beam of its light passed through a prism is thrown upon the wall in a wedge-shaped streak of rainbow-tinted colors. Fraunhofer, many years ago, found that this spectrum was crossed at irregular intervalsby a series of dark lines, of variable width and distance apart, of which he catalogued more than five hundred. These lines were subsequently found to correspond in the aggregate, in their position in the spectrum, with a series of bright lines of different colors which formed the separate spectra of various metals when burned, in vapor or powder, in the flame of an alcohol lamp. Each of these transverse lines was found to have a fixed and invariable position in the extended scale of the spectrum, and scarcely any lines of the different elements are alike; so that, when the spectrum is properly magnified under telescopic observation and the lines identified, we have the means of determining the presence or absence of such elements in the vaporous constitution of any incandescent body by examination of its spectrum. In this way many of our terrestrial elements are found to exist in the sun,—so many, in fact, that we know that the sun’s nucleus, or core, must be composed substantially of the same elements, the same sort of matter, as exists on earth,—that we are, in fact, “a chip of the old block.” But it was found—and this is the real basis of spectrum analysis—that if a certain metal or other element be burned in the flame of an alcohol lamp, and a more brilliant flame of the same metal or element burned in another lamp be observed through the first flame, it will be seen that, “while the general illumination of the spectrum is increased, the previous bright lines characterizing the element are now replaced by dark lines or lines relatively veryfaint; in a word, the spectrum characteristic of the given element is exactly reversed” (Appleton’s Cyclopædia, article “Spectrum Analysis”). We have referred to this fact above in considering the origin of sun-spots, showing that they are due to increased heat acting upon the core of the sun so as to volatilize an abnormally large proportion of the elements usually in a more condensed state upon the surface of the solar body beneath its hydrogen envelope. These vapors, thus raised in temperature, are driven upward by their volatilization into the incandescent atmosphere of hydrogen, and the vaporous matters in the higher strata thus produce the characteristic absorption bands of these elements, while the overheatedvapors, by a vast uprush from beneath, hurl aside the more highly heated hydrogen above to appear as faculæ around the sun-spot, the cooler upper layers of hydrogen following downward the subsiding vaporous metallic uprush as it sinks back beneath the photospheric level.1 Solar.Dark HeatRedOrangeYellowGreenBlueVioletActinic2 Sodium,3 Calcium.4 Hydrogen (Absorption Spectrum)5 Hydrogen (Bright Line Spectrum)Spectra of different elements compared with the solar spectrum, and showing reversal of hydrogen lines under special circumstances.It is obvious that by similar spectrum analysis we may determine to a large extent the constitution of the fixed stars and other self-luminous bodies of space and interpret the phenomena which they exhibit. We quote the following from the previously cited article in Appleton’s Cyclopædia, by Professor Proctor: “Spectroscopic analysis applied to the stars has shown that they resemble the sun in general constitution and condition. But characteristic differences exist, insomuch that the stars have been divided into four orders distinguished by their spectra. These are thus presented by Secchi, who examined more than five hundred star spectra: The first type is represented by Alpha Lyræ, Sirius, etc., and includes most of the stars shining with a white light, as Altair, Regulus, Rigel, the stars Beta, Gamma, Epsilon, Zeta, and Eta of Ursa Major, etc. These give a spectrum showing all the seven colors, and crossed usually by many lines, butalways by the four lines of hydrogen, very dark and strong. The breadth of these four lines indicates a very deep, absorptive stratum at a high temperature and at great pressure.Nearly half the starsobserved by Secchi [more than two hundred out of five hundred] showed this spectrum. The second type includes most of theyellow stars, as Capella, Pollux, Arcturus, Aldebaran, Alpha of Ursa Major, Procyon, etc. The Fraunhofer lines are well seen in the red and blue, but not so well in the yellow.The resemblance of this spectrum to the sunsuggests that stars of this type resemble the sun closely in physical constitution and condition. About one-third of the stars observed by Secchi [more than one hundred and fifty out of five hundred] showed this spectrum. The third type includes Antares, Alpha of Orion, and Alpha of Hercules, Beta of Pegasus, Mira, and most of the stars shining with a red light. The spectra show bands of lines; according to Secchi, there are shaded bands, but a more powerful spectroscope shows multitudes of fine lines. The spectra resemble somewhat thespectrum of a sun-spot, and Secchi has advanced the theory that these stars are covered in great part by spots like those of the sun. About one hundred [out of five hundred] of the observed stars belong to this type.” (It should be noted that the presence of sun-spots is no evidence of diminished heat in a sun; see Professor Proctor in his “Myths and Marvels of Astronomy,” article “Suns in Flames:” “It may be noticed, in passing, that it is by no means certain that the time when the sun is most spotted is the time when he gives out least light …. All the evidence we have tends to show that when the sun is most spotted his energies are most active. It is then that the colored flames leap to their greatest height and show their greatest brilliancy, then also that they show the most rapid and remarkablechanges of shape.”) … “The fourth type differs from the preceding in the arrangement and appearance of the bands. It includes only faint stars. A few stars, as Gamma of Cassiopeia, Eta of Argus, Beta of Lyra, etc., show thelines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself around which the hydrogen exists.”Reversal and neutralization of spectroscopic lines in spectrum of a variable star like Betelgeuse.—1, photosphere hotter than chromosphere; hydrogen lines dark. 2, chromosphere hotter than photosphere; hydrogen lines bright. 3, chromosphere and photosphere equally incandescent.All the above five hundred stars reveal the presence of hydrogen under precisely such conditions as conform to the general principle involved in the source and mode of solar energy as herein stated. But a single star (Betelgeuse) was observed by Huggins and Miller in England which showed the lines of sodium, magnesium, iron, bismuth, and calcium, “but found those of hydrogen wanting.” Of the spectrum of this gas, Professor Ball says, “The hydrogen spectrum appears to present a simplicity not found in the spectrum of any other gas, and therefore it is with great interest that we examine the spectra of the white stars, in whichthe dark lines of hydrogenare unusually strong and broad.” Referring to the new star in the Northern Crown, which burst forth in 1866, the same writer says, “The feature which made the spectrum of the new star essentially distinct from that of any other star that had been previously observed was the presence ofcertain bright linessuperposed on a spectrum with dark lines of one of the ordinary types. The position of certain ofthese lines showed that one of the luminous gases must be hydrogen.” Ofthis particular star (Betelgeuse) it is said (Proctor’s “Familiar Essays”), “Red stars and variable stars affect the neighborhood of the Milky Way or of well-marked star-streams. The constellation Orion is singularly rich in objects of this class. It is here that the strange ‘variable’ Betelgeuse lies. At present this star shows no sign of variation, but a few years ago it exhibited remarkable changes.” We thus see that Betelgeuse is a variable star, and it must have passed in its different variations between the limits of extreme brilliancy, in which the lines of hydrogen appear bright, and that of a less brilliant stage, in which they appear dark,—that is, as absorption bands. It has thus, in fact, run the gamut, so to speak, of color changes, and now occupies an intermediate position in the scale. In his article “Star unto Star,” the same writer says, “On this view we may fairly assume that the darkness of the hydrogen lines is a characteristic of stars at a much higher temperature than our sun and suns of the same class.” We have already seen that the spectra of stars of the fourth type—Appleton’s Cyclopædia, “Spectrum Analysis”—“show the lines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself.” Professor Dunkin says, in his work “The Midnight Sky,” “One of the conclusions drawn by Kirchhoff from these experiments is that each incandescent gasweakens, by absorption, rays of the same degree of refrangibility as those it emits; or, in other words, that the spectrum of each incandescent gasis reversed when this gas is traversed by rays of the same refrangibility emanating from an intensely luminous source which gives of itself a continuous spectrum like that of the sun.” … “The third division, including Betelgeuse, Antares, Alpha Herculis, and others of like color, seems to be affected by something peculiar in their physical composition,as if their photospheres contained a quantity of gas at a lower temperature than usual. The stars in this class have generally a ruddy tint, probably owing to their light having undergone some modification while passing through an absorbing atmosphere …. A great number of the stars in the third division are variable in their lustre.” We may therefore readily conclude that midway between the inverted lines which constitute the dark absorption bands and the faint spectra which show the bright lines of hydrogen direct there must be an atmosphere of glowing hydrogen superposed upon a deeper one in such proportion that it willnot reveal its presence in the spectroscope at all; for when the dark and light bands, which occupy precisely the same position in the spectrum, are of approximately equal intensity the result will obviously be the neutralization of both. That among a myriad suns, some with dark hydrogen lines and some with bright, there should occur occasionally an example corresponding to this point of divergence, and especially among variable stars, is not only to be expected, but is, in fact, confirmatory of the general hypothesis itself. It is an exception which emphatically proves the rule, when we can trace the operative cause which has produced it.

What, then, becomes of the light and heat flashed forth with eternal energy from the fiery waves of the sun’s incandescent atmosphere? Professor Ball (“In the High Heavens”) says, “Much of what has been said with regard to light may be repeated with regard to heat. We know that radiant heat consists of ethereal undulations of the same character as the waves of light. Hence we see that the heat or the light radiated from a glowing gas is mainly provided at the expense of the energy possessed by the molecules in virtue of their internal oscillations.” Conversely, of course, the ethereal undulations thus induced by high molecular motion in the heated gas or vapor must disappear in so-called absorption or transference by contact with other molecules, themselves devoid of such specific internal oscillations. The heat motion then disappears as heat by its conversion into work, just as the motion of a belt in a mill disappears in the work of the machine which it drives. One two-hundred-and-thirty-two-millionth part of the radiant solar energy, we know, is caught by the flying planets of our system in the forms of heat and light, adapted to sustain life and its continuedpotentiality, and we know that this solar energy is the sole source of all the development and maintenance of the planets as the possible abodes of organic life, past, present or future.

But what of the vast total, of which we consume so minute a fraction? It is true that, in addition to the planets, space is occupied by many small meteoric bodies, which manifest themselves to us as shooting stars and meteorites, but the mass of these is too trifling to be estimated. Professor Helmholtz, in his “Popular Scientific Lectures,” says, “According to Alexander Herschel’s estimates, each stone is, on an average, at a distance of four hundred and fifty miles from its neighbors.” When these bodies enter our atmosphere by force of the earth’s attraction they are heated by its atmospheric friction to incandescence, and in most cases are even volatilized before reaching the earth’s surface. The vast volumes of solar heat and light, however, are poured forth from the sun indiscriminately in all directions into illimitable space, wherein all the masses of concrete matter, including the stars, are relatively far less in volume than the flying motes of the purest morning air which sparkle in the flood of light sent forth by the rising sun. Is all the rest wasted? Professor Balfour Stewart, in his work “The Conservation of Energy,” says, “If this be the fate of the high-temperature energy of the universe, let us think for a moment what will happen to its visible energy. We have spoken already about a medium pervading space, the office of which appears to be to degrade and ultimatelyextinguish all differential motion, just as it tends to reduce and ultimately equalize all difference in temperature. Thus, the universe would ultimately become an equally heated mass, utterly worthless as far as the production of work is concerned, since such production depends upon difference of temperature.”

It is obvious that the starting-point taken by the author last quoted, but which, nevertheless, is in accordance with the views now generally prevalent, is diametrically opposed to that sought to be established in this work. Professor Stewart takes the sun’s inherent energy as the initial point of departure, and reasons from that as to the final consequence when all its light and heat shall have been distributed or dissipated into the attenuated medium which occupies space, and which will be thus slowly heated until all space has been raised in temperature to that of the last dying sun, when all will thenceforth remain unchanged and unchangeable, silent, dark, and dead, to all eternity. On the contrary, the purpose of the present work is to establish a directly opposite principle, based, however, on demonstrated scientific facts and not on theory, that the medium which pervades all space was originally in the same equally and universally potential state (with its molecules raised to a tension constituting an unstable equilibrium) in which, practically, Professor Stewart’s argument leaves it finally, and that this universal molecular energy of position was permanently maintained by the employment of the forces which afterwards,transformed into light and heat, were shed abroad by the sun in the work of again overcoming the intermolecular tension of cohesion, and that the light and heat of the sun are merely caught up again by these same or other molecules and successively employed in the same manner, while the planetary electrospheres utilize these same forces of internal tension in the generation of electricity, which, sent to the sun, is converted into light and heat, and these are again transferred to their original source. The rotation of the planets is the grand exciting cause, and the process, in its complete cycle of development, has live stages: first, planetary generation; second, transference by currents of electricity to the sun; third, conversion into light and heat; fourth, emission; and, fifth, reabsorption and conversion again into molecular energy of position. All space is thus found to be pervaded by extremely attenuated vapors, which contain the elemental constituents out of which suns and planets are evolved under favorable circumstances of development, and, among other vapors, aqueous vapor, and that these are the agency upon which the planetary electrospheres operate in their generation of electrical currents, and which vapors, in turn, by absorption of the solar energy of radiation, again transform this energy into mutually balanced electric potential, until it is once more disengaged as electricity by the rotating planetary electrospheres, and so on in a constant circuit forever repeated. It differs from perpetual motion, however, in that the planetary rotation is the externaland not the internal generative cause, since the electrical forces neither cause nor control these motions; they belong to the realm of gravity. The disassociation, moreover, is electrical and not chemical disassociation. The tensions are against cohesion and not against chemical affinity; are, in fact, similar to those which constitute our atmosphere a vast electrical reservoir; and the aqueous vapors, through all their changes, permanently remain as aqueous vapors, except those condensed portions disassociated by electrolytic action at the electrospheric poles, and which have no relation to the attenuated vapors of space, except in that the latter are their sources of supply. The process is analogous to what we see around us at all times in the atmosphere. While the process described by Professor Stewart resembles the emptying of the inherent water of a cloud, in the form of rain, into an ocean which never yields up its water again, so that, when the cloud has rained itself out, it is gone forever, the processes here sketched are like the vapors which are caught up by the heated air, carried over the thirsty lands, distributed in rain to fertilize and vivify them, then gathered in a thousand tiny rills from countless fountains, again descending to the sea and again carried up in vapor, and so on over and over in unceasing round. It is the difference between an old-fashioned flintlock musket and a modern magazine rifle, except that the magazine is always full.

This great ocean of space was primordially charged with these potential vapors; it is theconstitution of space itself. We are so accustomed to consider space as empty, and that it is nothingness, the antithesis of something or anything, that it is a negation or a blank, that it requires an effort to even think of it as a fully stocked establishment with all the goods necessary for use or ornament, in the latest styles and of prime quality, only not made up, and that all our suns and worlds are merely tailoring establishments where the operatives cut and fit and make them up to order. When more goods are wanted they have to go to the store.

Is space, then, eternal, and is this constant round of energies to be eternal? If one is eternal, so is the other, and surely nothing can be more eternal than space, and we cannot conceive of any other space than this space. Out of it came all created things, and so long as the orbs rotate without retardation, so long will these interchanges go on without impairment, and that they do so rotate is the necessary corollary of the fact that they ever began to rotate. If rotation, on the contrary, was imparted by special creative power, then the same power established the laws by which they rotate, and took cognizance of resistance as well. Whatever the impulse was, it still remains; whatever caused the rotation to begin maintains it; if the cause is eternal the rotation may be eternal; and, in any case, its period must be measured by cycles of æons, to which the allotted lifetime of a dying sun—a few million years, perhaps—is but as the sunburst of a morning-glory flower to the hoary age of a mighty planet. Compared with the popularview of the sun’s life-period, we may formulate the terms of an equation in which the sun’s mass, compared with the realms of infinite space, is as the sun’s lifetime—on a basis of contraction of his volume—to the lifetime which actually is to be. As one of the terms is practically infinite, so must be the answer to the problem. Professor Stewart says, “We cannot help believing that there is a material medium of some kind between the sun and the earth; indeed, the undulatory theory of light requires this belief.” It has already been shown that the transmission of electricity also requires it, but that there must be a medium quite different from the undulatory ether. Professor Proctor (“Mysteries of Time and Space”) says, “We may admit the possibility that the aqueous vapor and carbon compounds are present in stellar or interplanetary space.” Again he says, “Assuming, as we well may, that space is really occupied by attenuated vapors.” The same writer says further, “To this end all thoughtful study of the mechanism seems to tend (associating, perhaps, our visible universe with others, permeating it as the ether of space permeates the densest solids, and in turn with others so permeated by it); there may be that constant interchange, that perpetual harmony, of which Goethe sung:

‘Balanced worlds from change defending,While everywhere diffused is harmony unending.’ ”

‘Balanced worlds from change defending,

While everywhere diffused is harmony unending.’ ”

The light and heat poured forth from the sun are, as stated, in the form of radiated energy.They penetrate the attenuated vapors as far as vision extends, and doubtless farther, but they cannot reach the boundaries of space, for even the mind of man cannot reach those limits. Aqueous vapor absorbs heat; we know this without any demonstration, for the radiated heat of the earth is arrested by a veil of clouds, so that on cloudy nights frost will not form. So also the sun shining into water will raise its temperature, as in a glass globe, and such absorption of heat by aqueous vapors or water would be much more manifest were not a large part employed in loosening the tension of the constituent molecules, since, when thus employed, it is not manifest as sensible heat. Professor Tyndall, in “The Forms of Water,” states that “The quantity of heat which would raise the temperature of a pound of water one degree would raise the temperature of a pound of iron ten degrees.” Professor Stewart, in “The Conservation of Energy,” says, “That peculiar motion which is imparted by heat when absorbed into a body is, therefore, one variety of molecular energy …. Part of the energy of absorbed heat is spent in pulling asunder the molecules of the body under the attractive force which binds them together, and thus a store ofenergy of positionis laid up, which disappears again after the body is cooled.

“Heat will only be changed into work while it passes from a body of high temperature to one of low …. At very high temperatures it is possible that most compounds are decomposed, and thetemperature at which this takes place, for any compound, has been termed its temperature of disassociation.Heat energy is changed into electrical separationwhen tourmalines and certain other crystals are heated.” It may be added that it is also changed into electrical energy by the operation of all electrical machines, as molecular motions are all mutually interconvertible, and heat itself is only a mode of such motion. Of radiant energy, the same writer says, “This form of energy [radiant heat] is converted into absorbed heat whenever it falls upon an opaque substance … and heats it. It is a curious question to ask what becomes of theradiant lightfrom the sun that is not absorbed either by the planets of our system or by any of the stars. We can only reply to such a question that,as far as we can judge from our present knowledge, the radiant energy that is not absorbed must be conceived to be traversing space at the rate of one hundred and eighty-eight thousand miles a second.”

We know, of course, that aqueous vapors are partially opaque to heat rays, as the radiated heat of the earth is partially arrested by such vapors in the atmosphere, but they are apparently transparent to the rays of light. But we know that this cannot be entirely true in fact, for light rays only differ from heat rays in the comparative length of their waves or impulses, while rays of light are always accompanied—when emitted by a thermally incandescent body—by a much larger number of those of heat. As a body is raised in temperature radiant dark rays first appear; these being raised higher, becomevisible as light, and new dark rays are radiated behind them, and this continues till after the state of highest incandescence is reached and the invisible chemical rays beyond the spectrum appear. It is like a crowd surging forth in flight from the doors of a building; as the speed of those in front increases to a run, others follow more slowly in the mass, and as these gain speed others continue to follow, while the great mass of laggards still trails along in a lengthening line to the rear. The perception of light is itself merely due to the constitution of the optic apparatus of the observer, which only takes cognizance of vibrations radiated from the middle portion of the scale, just as the ear does with sounds, and not to any actual difference in their mode of production. That heat rays and light rays are identical in constitution can be readily shown by the experiment described by Professor Tyndall in his “Forms of Water,” in which an opaque screen of iodine solution in bisulphide of carbon was employed to arrest, in a beam of light, all the light waves (to which it is entirely opaque), while transmitting the dark rays. These non-luminous rays are then converged by a lens: “Let us, then, by means of our opaque solution, isolate our dark waves and converge them on the cotton. It explodes as before …. At the same dark focus sheets of platinum are raised to vivid redness; … a diamond is caused to glow like a star, being afterwards gradually dissipated.” Sir William Herschel (see article “Spectrum,” Appleton’s Cyclopædia) says, “If we call light those rays which illuminateobjects, and radiant heat those which heat bodies, it may be inquired whether light be essentially different from radiant heat. In answer to which I would suggest that we are not allowed by the rules of philosophizing to admit of two different causes to explain certain effects, if they may be accounted for by one.”… “Tyndall, by similar experiments, found that the thermal energy of the invisible radiation of a very powerful electric light is eight times that of the visible …. Seebeck showed that the position of maximum heat in the spectrum changes with the nature of the prism and sometimes occurs in the red.” Melconi, with prisms of alcohol and water, found it in the yellow. Athermic bands are also found in the heat-spectrum, corresponding to the Fraunhofer lines seen in the visible spectrum.

We may illustrate this successive development of more and more rapid light-waves by conceiving of a harp having musical strings of various length and thickness, but not strung up, so that, when swept by the hand, the vibrations are felt, but no musical tones are produced. If, now, all the strings are simultaneously and gradually stretched while under continuous vibration, we will first hear the hum of the lighter strings, but deep down in the scale; and as the tension gradually increases the pitch of these will rise higher and higher and be succeeded by other new tones below, until the whole register is simultaneously sounded. And if the tension be further increased, the vibrations of the upper strings will gradually grow so rapid that the ear can take no cognizance of them, correspondingto the invisible chemical rays of the spectrum, while the middle strings will be sounding loudly, and others will be slowly vibrating below the musical scale, but without sound, corresponding to the invisible heat rays. In addition to this gradual ascent of pitch along the scale, however, there is reason to believe that sympathetic vibrations are induced in the spectrum of thermal and chemical light corresponding to the over-tones in music and to those hidden rhythms which differentiate the “timbre” of one kind of musical instrument from that of another, so that a definite wave-length will not only repeat itself among adjacent molecules, but will give rise to harmonious vibrations quite different in amplitude and velocity. An example of this is found in some of the phenomena of phosphorescence and fluorescence, in which chemical rays totally invisible are able, under suitable conditions, to excite molecular movements corresponding to parts of the visible spectrum, and quite different in wave-lengths and in rapidity. This process is precisely the converse of what we perceive in thermal light; in the latter case the colors ascend, loaded with invisible heat rays; in the former they descend, loaded with invisible chemical rays, only noted, perhaps, by their actinic action on the photographic plate. Others, as the sulphide of calcium paints and the like, repeat their own vibrations for many hours, and we find in certain chemical salts of some rare metals, as lanthanum and cerium, the curious property of suddenly raising the whole scale, as in a recently introducedgas-lamp, in which a skeleton mantle of these oxides glows with a wondrously beautiful white light under the relatively low temperature of a small Bunsen burner; similar phenomena are manifested in the behavior of electric discharges in attenuated gases, as well as in what is known to children as “fox-fire,” wood undergoing slow decomposition in damp places, or in the self-luminous secretions (corresponding, perhaps, to ptomaines or like products) of glow-worms and other animals. If we ever—as we probably soon shall—reach that point where we can illuminate our dwellings with “cold candles,” as the inhabitants of tropical countries carry about a few fire-flies in a paper box for a lantern on dark nights, it must be by the study of these phenomena. But meantime “Old Sol” will continue to discharge his accumulating stores of both heat and light, for both these are essential, not only for use upon the planets, but throughout all the realms of space. In the transformation into and emission of his radiant energy the sun is not a chemical engine, but a mill,—one of those which “grind slowly, but they grind exceeding small.”

The difference between radiated thermal light and heat is obviously one of degree only and not of kind. The undulations of light may be compared to the thrust of a rapier, and the more massive waves of radiant heat to the blow of a bludgeon, but the same resistance which arrests the advance of the one must retard and finally arrest that of the other, if sufficiently extended. Within the limits of a space in which ProfessorStewart conceives that the first rays of light which ever flashed forth at the dawn of creation, in the primal æons of the universe, are still to this day, along their original lines of radiation, “traversing space at the rate of one hundred and eighty-eight thousand miles per second,” there must certainly be room enough and absorption enough (which even a few yards of mist will supply) to curb these runaway steeds somewhere along their lines of flaming passage. At that very point they are at work acting upon the molecules of the attenuated vapors of space, and assisting to re-establish the potential energy which has there been converted, into another form of force by the planetary rotations of the solar systems of those distant regions. By the law of the diffusion of gases, and that of the diffusion or transference of heat-energy from molecule to molecule, the vast realms of interstellar space must tend to be all brought into approximate uniformity of tensions, and the force abstracted at those points of space occupied by the relatively few and insignificant solar systems will be returned, not directly at the identical places where such solar systems may exist, but at every part of space to which their radiant energy extends. As we give from our own supplies to other systems for their support, so they, in turn, give back again to us. It is said that in the earliest days of creation the stars sang together; they still sing together, planets and suns, as

“Jura answers from her misty shroudBack to the joyous Alps, who call to her aloud.”

“Jura answers from her misty shroud

Back to the joyous Alps, who call to her aloud.”

When old Earth lifts his brimming beaker from the great crystal sea and drains it to the good health of all the stars of heaven, they each respond with fiery energy, and by their merry twinkle we may know how highly they appreciate the toast. We are all one family,—but what a family! Comets, planets, double stars, variable stars, stars of complementary colors, blue, yellow, orange, and red stars, stars which blaze up in sudden conflagration, apparently new stars, nebulæ half star and half vapor, nebulæ all vapor and others all stars, the vast milky-way like a wondrous river of hundreds of millions of solar systems, the insulated stars scattered through space like watchmen on the distant hills beyond the city walls, streams of stars, stars which are parting from each other in space like scattering families, and those which travel together in groups like pioneers in a strange country,—all these and doubtless other unknown types and forms compose this sidereal family. Will they fall into their categories as lawful subjects, so as to be properly classified in a single scheme of the visible order of creation, or shall we fail to interpret their apparent mysteries when we apply the same principles which have been successfully applied to the phenomena of our own solar system? Let us see.

In examining the sun, we find that a beam of its light passed through a prism is thrown upon the wall in a wedge-shaped streak of rainbow-tinted colors. Fraunhofer, many years ago, found that this spectrum was crossed at irregular intervalsby a series of dark lines, of variable width and distance apart, of which he catalogued more than five hundred. These lines were subsequently found to correspond in the aggregate, in their position in the spectrum, with a series of bright lines of different colors which formed the separate spectra of various metals when burned, in vapor or powder, in the flame of an alcohol lamp. Each of these transverse lines was found to have a fixed and invariable position in the extended scale of the spectrum, and scarcely any lines of the different elements are alike; so that, when the spectrum is properly magnified under telescopic observation and the lines identified, we have the means of determining the presence or absence of such elements in the vaporous constitution of any incandescent body by examination of its spectrum. In this way many of our terrestrial elements are found to exist in the sun,—so many, in fact, that we know that the sun’s nucleus, or core, must be composed substantially of the same elements, the same sort of matter, as exists on earth,—that we are, in fact, “a chip of the old block.” But it was found—and this is the real basis of spectrum analysis—that if a certain metal or other element be burned in the flame of an alcohol lamp, and a more brilliant flame of the same metal or element burned in another lamp be observed through the first flame, it will be seen that, “while the general illumination of the spectrum is increased, the previous bright lines characterizing the element are now replaced by dark lines or lines relatively veryfaint; in a word, the spectrum characteristic of the given element is exactly reversed” (Appleton’s Cyclopædia, article “Spectrum Analysis”). We have referred to this fact above in considering the origin of sun-spots, showing that they are due to increased heat acting upon the core of the sun so as to volatilize an abnormally large proportion of the elements usually in a more condensed state upon the surface of the solar body beneath its hydrogen envelope. These vapors, thus raised in temperature, are driven upward by their volatilization into the incandescent atmosphere of hydrogen, and the vaporous matters in the higher strata thus produce the characteristic absorption bands of these elements, while the overheatedvapors, by a vast uprush from beneath, hurl aside the more highly heated hydrogen above to appear as faculæ around the sun-spot, the cooler upper layers of hydrogen following downward the subsiding vaporous metallic uprush as it sinks back beneath the photospheric level.

1 Solar.Dark HeatRedOrangeYellowGreenBlueVioletActinic2 Sodium,3 Calcium.4 Hydrogen (Absorption Spectrum)5 Hydrogen (Bright Line Spectrum)Spectra of different elements compared with the solar spectrum, and showing reversal of hydrogen lines under special circumstances.

1 Solar.Dark HeatRedOrangeYellowGreenBlueVioletActinic

2 Sodium,

3 Calcium.

4 Hydrogen (Absorption Spectrum)

5 Hydrogen (Bright Line Spectrum)

Spectra of different elements compared with the solar spectrum, and showing reversal of hydrogen lines under special circumstances.

It is obvious that by similar spectrum analysis we may determine to a large extent the constitution of the fixed stars and other self-luminous bodies of space and interpret the phenomena which they exhibit. We quote the following from the previously cited article in Appleton’s Cyclopædia, by Professor Proctor: “Spectroscopic analysis applied to the stars has shown that they resemble the sun in general constitution and condition. But characteristic differences exist, insomuch that the stars have been divided into four orders distinguished by their spectra. These are thus presented by Secchi, who examined more than five hundred star spectra: The first type is represented by Alpha Lyræ, Sirius, etc., and includes most of the stars shining with a white light, as Altair, Regulus, Rigel, the stars Beta, Gamma, Epsilon, Zeta, and Eta of Ursa Major, etc. These give a spectrum showing all the seven colors, and crossed usually by many lines, butalways by the four lines of hydrogen, very dark and strong. The breadth of these four lines indicates a very deep, absorptive stratum at a high temperature and at great pressure.Nearly half the starsobserved by Secchi [more than two hundred out of five hundred] showed this spectrum. The second type includes most of theyellow stars, as Capella, Pollux, Arcturus, Aldebaran, Alpha of Ursa Major, Procyon, etc. The Fraunhofer lines are well seen in the red and blue, but not so well in the yellow.The resemblance of this spectrum to the sunsuggests that stars of this type resemble the sun closely in physical constitution and condition. About one-third of the stars observed by Secchi [more than one hundred and fifty out of five hundred] showed this spectrum. The third type includes Antares, Alpha of Orion, and Alpha of Hercules, Beta of Pegasus, Mira, and most of the stars shining with a red light. The spectra show bands of lines; according to Secchi, there are shaded bands, but a more powerful spectroscope shows multitudes of fine lines. The spectra resemble somewhat thespectrum of a sun-spot, and Secchi has advanced the theory that these stars are covered in great part by spots like those of the sun. About one hundred [out of five hundred] of the observed stars belong to this type.” (It should be noted that the presence of sun-spots is no evidence of diminished heat in a sun; see Professor Proctor in his “Myths and Marvels of Astronomy,” article “Suns in Flames:” “It may be noticed, in passing, that it is by no means certain that the time when the sun is most spotted is the time when he gives out least light …. All the evidence we have tends to show that when the sun is most spotted his energies are most active. It is then that the colored flames leap to their greatest height and show their greatest brilliancy, then also that they show the most rapid and remarkablechanges of shape.”) … “The fourth type differs from the preceding in the arrangement and appearance of the bands. It includes only faint stars. A few stars, as Gamma of Cassiopeia, Eta of Argus, Beta of Lyra, etc., show thelines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself around which the hydrogen exists.”

Reversal and neutralization of spectroscopic lines in spectrum of a variable star like Betelgeuse.—1, photosphere hotter than chromosphere; hydrogen lines dark. 2, chromosphere hotter than photosphere; hydrogen lines bright. 3, chromosphere and photosphere equally incandescent.

Reversal and neutralization of spectroscopic lines in spectrum of a variable star like Betelgeuse.—1, photosphere hotter than chromosphere; hydrogen lines dark. 2, chromosphere hotter than photosphere; hydrogen lines bright. 3, chromosphere and photosphere equally incandescent.

All the above five hundred stars reveal the presence of hydrogen under precisely such conditions as conform to the general principle involved in the source and mode of solar energy as herein stated. But a single star (Betelgeuse) was observed by Huggins and Miller in England which showed the lines of sodium, magnesium, iron, bismuth, and calcium, “but found those of hydrogen wanting.” Of the spectrum of this gas, Professor Ball says, “The hydrogen spectrum appears to present a simplicity not found in the spectrum of any other gas, and therefore it is with great interest that we examine the spectra of the white stars, in whichthe dark lines of hydrogenare unusually strong and broad.” Referring to the new star in the Northern Crown, which burst forth in 1866, the same writer says, “The feature which made the spectrum of the new star essentially distinct from that of any other star that had been previously observed was the presence ofcertain bright linessuperposed on a spectrum with dark lines of one of the ordinary types. The position of certain ofthese lines showed that one of the luminous gases must be hydrogen.” Ofthis particular star (Betelgeuse) it is said (Proctor’s “Familiar Essays”), “Red stars and variable stars affect the neighborhood of the Milky Way or of well-marked star-streams. The constellation Orion is singularly rich in objects of this class. It is here that the strange ‘variable’ Betelgeuse lies. At present this star shows no sign of variation, but a few years ago it exhibited remarkable changes.” We thus see that Betelgeuse is a variable star, and it must have passed in its different variations between the limits of extreme brilliancy, in which the lines of hydrogen appear bright, and that of a less brilliant stage, in which they appear dark,—that is, as absorption bands. It has thus, in fact, run the gamut, so to speak, of color changes, and now occupies an intermediate position in the scale. In his article “Star unto Star,” the same writer says, “On this view we may fairly assume that the darkness of the hydrogen lines is a characteristic of stars at a much higher temperature than our sun and suns of the same class.” We have already seen that the spectra of stars of the fourth type—Appleton’s Cyclopædia, “Spectrum Analysis”—“show the lines of hydrogen bright instead of dark, as though surrounded by hydrogen glowing with a heat more intense than that of the central orb itself.” Professor Dunkin says, in his work “The Midnight Sky,” “One of the conclusions drawn by Kirchhoff from these experiments is that each incandescent gasweakens, by absorption, rays of the same degree of refrangibility as those it emits; or, in other words, that the spectrum of each incandescent gasis reversed when this gas is traversed by rays of the same refrangibility emanating from an intensely luminous source which gives of itself a continuous spectrum like that of the sun.” … “The third division, including Betelgeuse, Antares, Alpha Herculis, and others of like color, seems to be affected by something peculiar in their physical composition,as if their photospheres contained a quantity of gas at a lower temperature than usual. The stars in this class have generally a ruddy tint, probably owing to their light having undergone some modification while passing through an absorbing atmosphere …. A great number of the stars in the third division are variable in their lustre.” We may therefore readily conclude that midway between the inverted lines which constitute the dark absorption bands and the faint spectra which show the bright lines of hydrogen direct there must be an atmosphere of glowing hydrogen superposed upon a deeper one in such proportion that it willnot reveal its presence in the spectroscope at all; for when the dark and light bands, which occupy precisely the same position in the spectrum, are of approximately equal intensity the result will obviously be the neutralization of both. That among a myriad suns, some with dark hydrogen lines and some with bright, there should occur occasionally an example corresponding to this point of divergence, and especially among variable stars, is not only to be expected, but is, in fact, confirmatory of the general hypothesis itself. It is an exception which emphatically proves the rule, when we can trace the operative cause which has produced it.

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