CHAPTER XXI

“Very bright, very large; oval; very gradually pretty, much brighter in the middle; a beautiful nebula; it has very much the resemblance to the Nubecula Major itself as seen with the naked eye, but it is far brighter and more impressive in its general aspect as if it were doubled in intensity. Note—July 29, 1837. I well remember this observation, it was the result of repeated comparisons between the object seen in the telescope and the actual nubecula as seen high in the sky on the meridian, and no vague estimate carelessly set down. And who can say whether in this object, magnified and analysed by telescopes infinitely superior to what we now possess, there may not exist all the complexity of detail that the nubecula itself presents to our examination?”[458]

The late Lord Kelvin, in a remarkable address delivered before the Physical Science Section of the British Association at its meeting at Glasgow in 1901, considered the probable quantity of matter contained in our Visible Universe. He takes a sphere of radius represented by the distance of a star having a parallax of one-thousandth of a second (or about 3000 years’ journey for light), and he supposes that uniformly distributed within this sphere there exists a mass of matter equal to 1000 million times the sun’s mass. With these data he finds that a body placed originally at the surface of the sphere would in 5 million years acquire by gravitational force a velocity of about 12½ miles a second, and after 25 million of years a velocity of about 67 miles a second. As these velocities are of the same order as the observed velocities among the stars, Lord Kelvin concludes that thereisprobably as much matter in our universe as would be represented by a thousand million suns. If we assumed a mass of ten thousand suns the velocities would be much too high. The most probable estimate of the total number of the visible stars is about 100 millions; so that if Lord Kelvin’s calculations are correct we seem bound to assume that space contains a number of dark bodies. The nebulæ, however, probably contain vast masses of matter, and this may perhaps account—partially, at least—for the large amount ofmatter estimated by Lord Kelvin. (See Chapter on “Nebulæ.”)

In some notes on photographs of the Milky Way, Prof. Barnard says with reference to the great nebula near ρ Ophiuchi, “The peculiarity of this region has suggested to me the idea that the apparently small stars forming the ground work of the Milky Way here, are really very small bodies compared with our own sun”; and again, referring to the region near β Cygni, “One is specially struck with the apparent extreme smallness of the general mass of the stars in this region.” Again, with reference to χ Cygni, he says, “The stars here also are remarkably uniform in size.”[459]

Eastman’s results for parallax seem to show that “the fainter rather than the brighter stars are nearest to our system.” But this apparent paradox is considered by Mr. Monck to be very misleading;[460]and the present writer holds the same opinion.

Prof. Kapteyn finds “that stars whose proper motions exceed 0″·05 are not more numerous in the Milky Way than in other parts of the sky; or, in other words, if only the stars having proper motions of 0″·05 or upwards were mapped, there would be no aggregation of stars showing the existence of the Milky Way.”[461]

With reference to the number of stars visible on photographs, the late Dr. Isaac Roberts says—

“So far as I am able at present to judge, under the atmospheric conditions prevalent in this country, the limit of the photographic method of delineation will be reached at stellar, or nebular, light of the feebleness of about 18th-magnitude stars. The reason for this inference is that the general illumination of the atmosphere by starlight concentrated upon a film by the instrument will mask the light of objects that are fainter than about 18th-magnitude stars.”[462]

With reference to blank spaces in the sky, the late Mr. Norman Pogson remarked—

“Near S Ophiuchi we find one of the most remarkable vacuities in this hemisphere—an elliptic space of about 65′ in length in the direction of R.A., and 40′ in width, in which there existsnostar larger than the 13th magnitude ... it is impossible to turn a large telescope in that direction and, if I may so express it, view such black darkness, without a feeling that we are here searching into the remote regions of space, far beyond the limits of our own sidereal system.”[463]

Prof. Barnard describes some regions in the constellation Taurus containing “dark lanes” in a groundwork of faint nebulosity. He gives two beautiful photographs of the regions referred to, and says that the dark holes and lanes areapparently darker than the sky in the immediate vicinity. He says, “A very singular feature in this connection is that the stars also are absent in general from the lanes.” A close examination of these photographs has given the present writer the impression that the dark lanes and spots areinthe nebulosity, and that the nebulosity is mixed up with the stars. This would account for the fact that the stars are in general absent from the dark lanes. For if there is an intimate relation between the stars and the nebulosity, it would follow that where there is no nebulosity in this particular region there would be no stars. Prof. Barnard adds that the nebulosity is easily visible in a 12-inch telescope.[464]

With reference to the life of the universe, Prof. F. R. Moulton well says—

“The lifetime of a man seems fairly long, and the epoch when Troy was besieged, or when the Pharaohs piled up the pyramids in the valley of the Nile, or when our ancestors separated on the high plateaux of Asia, seems extremely remote, but these intervals are only moments compared to the immense periods required for geological evolutions and the enormously greater ones consumed in the developement of worlds from widely extended nebulous masses. We recognize the existence of only those forces whose immediate consequences are appreciable, and it may be that those whose effects are yet unseen are really of the highest importance. A little creature whoselife extended over only two or three hours of a summer’s day might be led, if he were sufficiently endowed with intelligence, to infer that passing clouds were the chief influence at work in changing the climate instead of perceiving that the sun’s slow motion across the sky would bring on the night and its southward motion the winter.”[465]

In a review of my bookAstronomical EssaysinThe Observatory, September, 1907, the following words occur. They seem to form a good and sufficient answer to people who ask, What is there beyond our visible universe? “If the stellar universe is contained in a sphere of say 1000 stellar units radius, what is there beyond? To this the astronomer will reply that theories and hypotheses are put forward for the purpose of explaining observed facts; when there are no facts to be explained, no theory is required. As there are no observed facts as to what exists beyond the farthest stars, the mind of the astronomer is a complete blank on the subject. Popular imagination can fill up the blank as it pleases.” With these remarks I fully concur.

In his address to the British Association, Prof. G. H. Darwin (now Sir George Darwin) said—

“Man is but a microscopic being relatively to astronomical space, and he lives on a puny planet circling round a star of inferior rank. Does it not, then, seem futile to imagine that he can discoverthe origin and tendency of the Universe as to expect a housefly to instruct us as to the theory of the motions of the planets? And yet, so long as he shall last, he will pursue his search, and will no doubt discover many wonderful things which are still hidden. We may indeed be amazed at all that man has been able to find out, but the immeasurable magnitude of the undiscovered will throughout all time remain to humble his pride. Our children’s children will still be gazing and marvelling at the starry heavens, but the riddle will never be read.”

The ancient philosopher Lucretius said—

“Globed from the atoms falling slow or swiftI see the suns, I see the systems liftTheir forms; and even the system and the sunsShall go back slowly to the eternal drift.”[466]

But it has been well said that the structure of the universe “has a fascination of its own for most readers quite apart from any real progress which may be made towards its solution.”[467]

The Milky Way itself, Mr. Stratonoff considers to be an agglomeration of immense condensations, or stellar clouds, which are scattered round the region of the galactic equator. These clouds, or masses of stars, sometimes leave spaces between them, and sometimes they overlap, and in this way he accounts for the great rifts, like the Coal Sack, which allow us to see through this greatcircle of light. He finds other condensations of stars; the nearest is one of which our sun is a member, chiefly composed of stars of the higher magnitudes which “thin out rapidly as the Milky Way is approached.” There are other condensations: one in stars of magnitudes 6·5 to 8·5; and a third, farther off, in stars of magnitudes 7·6 to 8. These may be called opera-glass, or field-glass stars.

Stratonoff finds that stars with spectra of the first type (class A, B, C, and D of Harvard) which include the Sirian and Orion stars, are principally situated near the Milky Way, while those of type II. (which includes the solar stars) “are principally condensed in a region coinciding roughly with the terrestrial pole, and only show a slight increase, as compared with other stars, as the galaxy is approached.”[468]

Prof. Kapteyn thinks that “undoubtedly one of the greatest difficulties, if not the greatest of all, in the way of obtaining an understanding of the real distribution of the stars in space, lies in our uncertainty about the amount of loss suffered by the light of the stars on its way to the observer.”[469]He says, “There can be little doubt in my opinion, about the existence of absorption in space, and I think that even a good guess as to the order of its amount can be made. For, firstwe know that space contains an enormous mass of meteoric matter. This matter must necessarily intercept some part of the star-light.”

This absorption, however, seems to be comparatively small. Kapteyn finds a value of 0·016 (about1⁄60th) of a magnitude for a star at a distance corresponding to a parallax of one-tenth of a second (about 33 “light years”). This is a quantity almost imperceptible in the most delicate photometer. But for very great distances—such as 3000 “light years”—the absorption would evidently become very considerable, and would account satisfactorily for the gradual “thinning out” of the fainter stars. If this were fully proved, we should have to consider the fainter stars of the Milky Way to be in all probability fairly large suns, the light of which is reduced by absorption.

That some of the ancients knew that the Milky Way is composed of stars is shown by the following lines translated from Ovid:—

“A way there is in heaven’s extended plainWhich when the skies are clear is seen belowAnd mortals, by the name of Milky, know;The groundwork is of stars, through which the roadLies open to great Jupiter’s abode.”[470]

From an examination of the distribution of the faint stars composing the Milky Way, and those shown in Argelander’s charts of stars down to the9½ magnitude, Easton finds that there is “a real connection between the distribution of 9th and 10th magnitude stars, and that of the faint stars of the Milky Way, and that consequently the faint or very faint stars of the galactic zone are at a distance which does not greatly exceed that of the 9th and 10th magnitude stars.”[471]A similar conclusion was, I think, arrived at by Proctor many years ago. Now let us consider the meaning of this result. Taking stars of the 15th magnitude, if their faintness were merely due to greater distance, their actual brightness—if of the same size—would imply that they are at 10 times the distance of stars of the 10th magnitude. But if at the same distance from us, a 10th magnitude star would be 100 times brighter than a 15th magnitude star, and if of the same density and “intrinsic brightness” (or luminosity of surface) the 10th magnitude would have 10 times the diameter of the fainter star, and hence its volume would be 1000 times greater (103), and this great difference is not perhaps improbable.

The constitution of the Milky Way is not the same in all its parts. The bright spot between β and γ Cygni is due to relatively bright stars. Others equally dense but fainter regions in Auriga and Monoceros are only evident in stars of the 8th and 9th magnitude, and the light of the well-known luminous spot in “Sobieski’s Shield,”closely south of λ Aquilæ, is due to stars below magnitude 9½.

The correspondence in distribution between the stars of Argelander’s charts and the fainter stars of the Milky Way shows, as Easton points out, that Herschel’s hypothesis of a uniform distribution of stars of approximately equal size is quite untenable.

It has been suggested that the Milky Way may perhaps form a ring of stars with the sun placed nearly, but not exactly, in the centre of the ring. But were it really a ring of uniform width with the sun eccentrically placed within it, we should expect to find the Milky Way wider at its nearest part, and gradually narrowing towards the opposite point. Now, Herschel’s “gages” and Celoria’s counts show that the Galaxy is wider in Aquila than in Monoceros. This is confirmed by Easton, who says, “for the faint stars taken as a whole, the Milky Way is widest in its brightest part” (the italics are Easton’s). From this we should conclude that the Milky Way is nearer to us in the direction of Aquila than in that of Monoceros. Sir John Herschel suggested that the southern parts of the galactic zone are nearer to us on account of their greaterbrightnessin those regions.[472]But greater width is a safer test of distance than relative brightness. For it may be easily shown than theintrinsicbrightness of anarea containing a large number of stars would be the same foralldistances (neglecting the supposed absorption of light in space). For suppose any given area crowded with stars to be removed to a greater distance. The light of each star would be diminished inversely as the square of the distance. But the given area would also be diminisheddirectlyas the square of the distance, so we should have a diminished amount of light on an equally diminished area, and hence the intrinsic brightness, or luminosity of the area per unit of surface, would remain unaltered. The increased brightness of the Milky Way in Aquila is accounted for by the fact that Herschel’s “gages” show an increased number of stars, and hence the brightness in Aquila and Sagittarius does not necessarily imply that the Milky Way is nearer to us in those parts, but that it is richer in small stars than in other regions.

Easton is of opinion that the annular hypothesis of the Milky Way is inconsistent with our present knowledge of the galactic phenomena, and he suggests that its actual constitution resembles more that of a spiral nebula.[473]On this hypothesis the increase in the number of stars in the regions above referred to may be due to our seeing one branch of the supposed “two-branched spiral” projected on another branch of the same spiral. This seems supported by Sir John Herschel’sobservations in the southern hemisphere, where he found in some places “a tissue as it were of large stars spread over another of very small ones, the immediate magnitudes being wanting.” Again, portions of the spiral branches may be richer than others, as photographs of spiral nebulæ seem to indicate. Celoria, rejecting the hypothesis of a single ring, suggests the existence oftwogalactic rings inclined to each other at an angle of about 20°, one of these including the brighter stars, and the other the fainter. But this seems to be a more artificial arrangement then the hypothesis of a spiral. Further, the complicated structure of the Milky Way cannot be well explained by Celoria’s hypothesis of two distinct rings one inside the other. From analogy the spiral hypothesis seems much more probable.

Considering the Milky Way to represent a colossal spiral nebula viewed from a point not far removed from the centre of the spiral branches, Easton suggests that the bright region between β and γ Cygni, which is very rich in comparatively bright stars, may possibly represent the “central accumulations of the Milky Way,” that is, the portion corresponding to the nucleus of a spiral nebula. If this be so, this portion of the Milky Way should be nearer to us than others. Easton also thinks that the so-called “solar cluster” of Gould, Kapteyn, and Schiaparelli may perhaps be “the expression ofthe central condensation of the galactic system itself, composed of the most part of suns comparable with our own, and which would thus embrace most of the bright stars to the 9th or 10th magnitude. The distance of the galactic streams and convolutions would thus be comparable with the distances of these stars.” He thinks that the sun lies within a gigantic spiral, “in a comparatively sparse region between the central nucleus and Orion.”

Scheiner thinks that “the irregularities of the Milky Way, especially in streams, can be quite well accounted for, as Easton has attempted to do, if they are regarded as a system of spirals, and not as a ring system.”

Evidence in favour of the spiral hypothesis of the Milky Way, as advocated by Easton and Scheiner, may be found in Kapteyn’s researches on the proper motions of the stars. This eminent astronomer finds that stars with measurable proper motions—and therefore in all probability relatively near the earth—have mostly spectra of the solar type, and seem to cluster round “a point adjacent to the sun, in total disregard to the position of the Milky Way,” and that stars with little or no proper motion collect round the galactic plain. He is also of opinion that the Milky Way resembles the Andromeda nebula, “the globular nucleus representing the solar cluster, and the far spreading wings or whorls thecompressed layer of stars enclosed by the rings of the remote Galaxy.”

With reference to the plurality of inhabited worlds, it has been well said by the ancient writer Metrodorus (third centuryB.C.), “The idea that there is but a single world in all infinitude would be as absurd as to suppose that a vast field had been formed to produce a single blade of wheat.”[474]With this opinion the present writer fully concurs.

General

Theachievements of Hipparchus in astronomy were very remarkable, considering the age in which he lived. He found the amount of the apparent motion of the stars due to the precession of the equinoxes (of which he was the discoverer) to be 59″ per annum. The correct amount is about 50″. He measured the length of the year to within 9 minutes of its true value. He found the inclination of the ecliptic to the plane of the equator to be 23° 51′. It was then 23° 46′—as we now know by modern calculations—so that Hipparchus’ estimation was a wonderfully close approximation to the truth. He computed the moon’s parallax to be 57′, which is about its correct value. He found the eccentricity of the sun’s apparent orbit round the earth to be one twenty-fourth, the real value being then about one-thirteenth. He determined other motions connected with the earth and moon; and formed a catalogue of 1080 stars. All this work has earned for him the well-merited title of “The Father of Astronomy.”[475]

The following is a translation of a Greek passage ascribed to Ptolemy: “I know that I am mortal and the creature of a day, but when I search out the many rolling circles of the stars, my feet touch the earth no longer, but with Zeus himself I take my fill of ambrosia, the food of the gods.”[476]This was inscribed (in Greek) on a silver loving cup presented to the late Professor C. A. Young, the famous American astronomer.[477]

Some curious and interesting phenomena are recorded in the old Chinese Annals, which go back to a great antiquity. In 687B.C.“a night” is mentioned “without clouds and without stars” (!) This may perhaps refer to a total eclipse of the sun; but if so, the eclipse is not mentioned in the Chinese list of eclipses. In the year 141B.C., it is stated that the sun and moon appeared of a deep red colour during 5 days, a phenomenon which caused great terror among the people. In 74B.C., it is related that a star as large as the moon appeared, and was followed in its motion by several stars of ordinary size. This probably refers to an unusually large “bolide” or “fireball.” In 38B.C., a fall of meteoric stones is recorded “of the size of a walnut.” InA.D.88, another fall of stones is mentioned. InA.D.321, sun-spots were visible to the naked eye.

Homer speaks of a curious darkness which occurred during one of the great battles in the last year of the Trojan war. Mr. Stockwell identifies this with an eclipse of the sun which took place on August 28, 1184B.C.An eclipse referred to by Thucydides as having occurred during the first year of the Peloponnesian War, when the darkness was so great that some stars were seen, is identified by Stockwell with a total eclipse of the sun, which took place on August 2, 430B.C.

A great eclipse of the sun is supposed to have occurred in the year 43 or 44B.C., soon after the death of Julius Cæsar. Baron de Zach and Arago mention it as the first annular eclipse on record. But calculations show that no solar eclipse whatever, visible in Italy, occurred in either of these years. The phenomenon referred to must therefore have been of atmospherical origin, and indeed this is suggested by a passage in Suetonius, one of the authors quoted on the subject.

M. Guillaume thinks that the ninth Egyptian plague, the thick “darkness” (Exodus x. 21-23), may perhaps be explained by a total eclipse of the sun which occurred in 1332B.C.It is true that the account states that the darkness lasted “three days,” but this, M. Guillaume thinks, may be due to an error in the translation.[478]This explanation, however, seems very improbable.

According to Hind, the moon was eclipsed onthe generally received date of the Crucifixion,A.D.33, April 3. He says, “I find she had emerged from the earth’s dark shadow a quarter of an hour before she rose at Jerusalem (6h36mp.m.); but the penumbra continued upon her disc for an hour afterwards.” An eclipse could not have had anything to do with the “darkness over all the land” during the Crucifixion. For this lasted for three hours, and the totality of a solar eclipse can only last a few minutes at the most. As a matter of fact the “eclipse of Phlegon,” a partial one (A.D.29, November 24) was “the only solar eclipse that could have been visible in Jerusalem during the period usually fixed for the ministry of Christ.”

It is mentioned in the Anglo-Saxon Chronicle that a total eclipse of the sun took place in the year after King Alfred’s great battle with the Danes. Now, calculation shows that this eclipse occurred on October 29, 878A.D.King Alfred’s victory over the Danes must, therefore, have taken place in 877A.D., and his death probably occurred in 899A.D.This solar eclipse is also mentioned in the Annals of Ulster. From this it will be seen that in some cases the dates of historical events can be accurately fixed by astronomical phenomena.

It is stated by some historians that an eclipse of the sun took place on the morning of the battle ofCrecy, August 26, 1346. But calculation shows that there was no eclipse of the sun visible in England in that year. At the time of the famous battle the moon had just entered on her first quarter, and she was partially eclipsed six days afterwards—that is on the 1st of September. The mistake seems to have arisen from a mistranslation of the old French wordesclistre, which means lightning. This was mistaken foresclipse. The account seems to indicate that there was a heavy thunderstorm on the morning of the battle.

A dark shade was seen on the waning moon by Messrs. Hirst and J. C. Russell on October 21, 1878, “as dark as the shadow during an eclipse of the moon.”[479]If this observation is correct, it is certainly most difficult to explain. Another curious observation is recorded by Mr. E. Stone Wiggins, who says that a partial eclipse of the sun by a dark body was observed in the State of Michigan (U.S.A.) on May 16, 1884, at 7 p.m. The “moon at that moment was 12 degrees south of the equator and the sun as many degrees north of it.” The existence of a dark satellite of the earth has been suggested, but this seems highly improbable.

The sun’s corona seems to have been first noticed in the total eclipse of the sun which occurred at the death of the Roman emperorDomitian,A.D.95. Philostratus in hisLife of Apolloniussays, with reference to this eclipse, “In the heavens there appeared a prodigy of this nature: a certaincoronaresembling the Iris surrounded the orb of the sun, and obscured its light.”[480]In more modern times the corona seems to have been first noticed by Clavius during the total eclipse of April 9, 1567.[481]Kepler proved that this eclipse was total, not annular, so that the ring seen by Clavius must have been the corona.

With reference to the visibility of planets and stars during total eclipses of the sun; in the eclipse of May 12, 1706, Venus, Mercury, and Aldebaran, and several other stars were seen. During the totality of the eclipse of May 3, 1715, about twenty stars were seen with the naked eye.[482]At the eclipse of May 22, 1724, Venus and Mercury, and a few fixed stars were seen.[483]The corona was also noticed. At the eclipse of May 2, 1733, Jupiter, the stars of the “Plough,” Capella, and other stars were visible to the naked eye; and the corona was again seen.[483]

During the total eclipses of February 9, 1766, June 24, 1778, and June 16, 1806, the corona was again noticed. But its true character was then unknown.

At the eclipse of July 8, 1842, it was noticed byobservers at Lipesk that the stars Aldebaran and Betelgeuse (α Orionis), which are usually red, “appeared quite white.”[484]

There will be seven eclipses in the years 1917, 1935, and 1985. In the year 1935 there will be five eclipses of the sun, a rare event; and in 1985 there will be three total eclipses of the moon, a most unusual occurrence.[485]

Among the ancient Hindoos, the common people believed that eclipses were caused by the interposition of a monstrous demon called Raha. This absurd idea, and others equally ridiculous, were based on declarations in their sacred books, and no pious Hindoo would think of denying it.

The following cases of darkenings of the sun are given by Humboldt:—

According to Plutarch the sun remained pale for a whole year at the death of Julius Cæsar, and gave less than its usual heat.[486]

A sun-darkening lasting for two hours is recorded on August 22, 358A.D., before the great earthquake of Nicomedia.

In 360A.D.there was a sun-darkening from early morn till noon. The description given by the historians of the time corresponds to an eclipse of the sun, but the duration of the obscurity is inexplicable.

In 409A.D., when Alaric lay siege to Rome,“there was so great a darkness that the stars were seen by day.”

In 536A.D.the sun is said to have been darkened for a year and two months!

In 626A.D., according to Abul Farag, half the sun’s disc was darkened for eight months!

In 934A.D.the sun lost its brightness for two months in Portugal.

In 1090A.D.the sun was darkened for three hours.

In 1096, sun-spots were seen with the naked eye on March 3.

In 1206A.D.on the last day of February, “there was complete darkness for six hours, turning the day into night.” This seems to have occurred in Spain.

In 1241 the sun was so darkened that stars could be seen at 3 p.m. on Michaelmas day. This happened in Vienna.[487]

The sun is said to have been so darkened in the year 1547A.D.for three days that stars were visible at midday. This occurred about the time of the battle of Mühlbergh.[488]

Some of these darkenings may possibly have been due to an enormous development of sun-spots; but in some cases the darkness is supposed by Chladni and Schnurrer to have been caused by “the passage of meteoric masses before the sun’s disc.”

The first observer of a transit of Venus was Jeremiah Horrocks, who observed the transit of November 24 (O.S.), 1639. He had previously corrected Kepler’s predicted time of the transit from 8h8ma.m. at Manchester to 5h57mp.m. At the end of 1875 a marble scroll was placed on the pedestal of the monument of John Conduitt (nephew of Sir Isaac Newton, and who adopted Horrocks’ theory of lunar motions) at the west end of the nave of Westminster Abbey, bearing this inscription from the pen of Dean Stanley—

The transit of Venus which occurred in 1761 was observed on board ship(!) by the famous but unfortunate French astronomer Le Gentil. The ship was the frigateSylphide, sent to the help of Pondicherry (India) which was then being besieged by the English. Owing to unfavourable winds theSylphidewas tossed about from March 25, 1761, to May 24 of the same year. When, on the later date, off the coast of Malabar, the captain of the frigate learned that Pondicherry had been captured by the English, the vessel returned to the Isle of France, where it arrived on June 23, after touching at Point de Galle on May 30. It was between these two places that Le Gentil made his observations of the transit of Venus under such unfavourable conditions. He had an object-glass of 15 feet (French) focus, and this he mounted in a tube formed of “four pine planks.” This rough instrument was fixed to a small mast set up on the quarter-deck and worked by ropes. The observations made under such curious conditions, were not, as may be imagined, very satisfactory. As another transit was to take place on June 3, 1769, Le Gentil made the heroic resolution of remaining in the southern hemisphere to observe it! This determination was duly carried out, but his devotion to astronomy was not rewarded; for on the day of the long waited for transit the sky at Pondicherry (where he had gone to observe it) was clouded overduring the whole phenomenon, “although for many days previous the sky had been cloudless.” To add to his feeling of disappointment he heard that at Manilla, where he had been staying some time previously, the sky was quite clear, and two of his friends there had seen the transit without any difficulty.[490]Truly the unfortunate Le Gentil was a martyr to science.

The famous German astronomer Bessel once said “that a practical astronomer could make observations of value if he had only a cart-wheel and a gun barrel”; and Watson said that “the most important part of the instrument is the person at the small end.”[491]

With reference to Father Hell’s supposed forgery of his observations of the transit of Venus in 1769, and Littrow’s criticism of some of the entries in Hell’s manuscript being corrected with a different coloured ink, Professor Newcomb ascertained from Weiss that Littrow was colour blind, and could not distinguish between the colour of Aldebaran and the whitest star. Newcomb adds, “For half a century the astronomical world had based an impression on the innocent but mistaken evidence of a colour-blind man respecting the tint of ink in a manuscript.”

It is recorded that on February 26,B.C.2012, the moon, Mercury, Venus, Jupiter, and Saturn,were in the same constellation, and within 14 degrees of each other. On September 14, 1186A.D., the sun, moon, and all the planets then known, are said to have been situated in Libra.[492]

In the Sanscrit epic poem, “The Ramaya,” it is stated that at the birth of Rama, the moon was in Cancer, the sun in Aries, Mercury in Taurus, Venus in Pisces, Mars in Capricornus, Jupiter in Cancer, and Saturn in Libra. From these data, Mr. Walter R. Old has computed that Rama was born on February 10, 1761B.C.[493]

A close conjunction of Mars and Saturn was observed by Denning on September 29, 1889, the bright star Regulus (α Leonis) being at the time only 47′ distant from the planets.[494]

An occultation of the Pleiades by the moon was observed by Timocharis at Alexandria on January 29, 282B.C.Calculations by Schjellerup show that Alcyone (η Tauri) was occulted; but the exact time of the day recorded by Timocharis differs very considerably from that computed by Schjellerup.[495]Another occultation of the Pleiades is recorded by Agrippa in the reign of Domitian. According to Schjellerup the phenomenon occurred on November 29,A.D.92.

“Kepler states that on the 9th of January, 1591,Mæstlin and himself witnessed an occultation of Jupiter by Mars. The red colour of the latter on that occasion plainly indicated that it was the inferior planet.”[496]That is, that Mars was nearer to the sun than Jupiter. But as the telescope had not then been invented, this may have been merely a near approach of the two planets.

According to Kepler, Mæstlin saw an occultation of Mars by Venus on October 3, 1590. But this may also have been merely a near approach.[496]

A curious paradox is that one can discover an object without seeing it, and see an object without discovering it! The planet Neptune was discovered by Adams and Leverrier by calculation before it was seen in the telescope by Galle; and it was actually seen by Lalande on May 8 and 10, 1795, but he took it for astarand thus missed the discovery. In fact, hesawthe planet, but did notdiscoverit. It actually appears as a star of the 8th magnitude in Harding’s Atlas (1822). The great “new star” of February, 1901, known as Nova Persei, was probably seen by some people before its discovery was announced; and it was actually noticed by a well-known American astronomer, who thought it was some bright star with which he was not familiar! But this did not amount to a discovery. Any one absolutely ignorant of astronomy might have made the same observation. An object must beidentifiedas anewobject before a discovery can be claimed. Some years ago a well-known Irish naturalist discovered a spider new to science, and after its discovery he found that it was common in nearly every house in Dublin! But this fact did not detract in the least from the merit of its scientific discovery.

There is a story of an eminent astronomer who had been on several eclipse expeditions, and yet was heard to remark that he had never seen a total eclipse of the sun. “But your observations of several eclipses are on record,” it was objected. “Certainly, I have on several occasions made observations, but I have always been too busy to look at the eclipse.” He was probably in a dark tent taking photographs or using a spectroscope during the totality. This was observing an eclipse without seeing it!

Humboldt gives the credit of the invention of the telescope to Hans Lippershey, a native of Wesel and a spectacle-maker at Middleburgh; to Jacob Adreaansz, surnamed Metius, who is also said to have made burning-glasses of ice; and to Zachariah Jansen.[497]

With reference to the parabolic figure of the large mirrors of reflecting telescopes, Dr. Robinson remarked at the meeting of the British Association at Cork in 1843, “between the spherical and parabolic figures the extreme difference is soslight, even in the telescope of 6-feet aperture [Lord Rosse’s] that if the two surfaces touched at their vertex, the distance at the edge would not amount to the1⁄10000of an inch, a space which few can measure, and none without a microscope.”[498]

In the year 1758, Roger Long, Lowndean Professor of Astronomy at Cambridge, constructed an “orrery” on a novel principle. It was a hollow metal sphere of about 18 feet in diameter with its fixed axis parallel to the earth’s axis. It was rotated, by means of a winch and rackwork. It held about thirty persons in its interior, where astronomical lectures were delivered. The constellations were painted on the interior surface; and holes pierced through the shell and illuminated from the outside represented the stars according to their different magnitudes. This ingenious machine was much neglected for many years, but was still in existence in Admiral Smyth’s time, 1844.[499]

A “temporary star” is said to have been seen by Hepidanus in the constellation Aries in either 1006 or 1012A.D.The late M. Schönfeld, a great authority on variable stars, found from an Arabic and Syrian chronicle that 1012 is the correct year (396 of the Hegira), but that the word translated Aries would by a probable emendation meanScorpio. The word in the Syrian record is not the word for Aries.[500]

Mr. Heber D. Curtis finds that the faintest stars mentioned in Ptolemy’s Catalogue are about 5·38 magnitude on the scale of the HarvardPhotometric Durchmustering.[501]Heis and Houzeau saw stars of 6-7 magnitude (about 6·4 on Harvard scale). The present writer found that he could see most of Heis’ faintest stars in the west of Ireland (Co. Sligo) without optical aid (except short-sighted spectacles).

With reference to the apparent changes in the stellar heavens produced by the precession of the equinoxes, Humboldt says—

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