HINTS TO AMATEURS IN ASTRONOMY RESPECTING THE CONSTRUCTION OF TELESCOPES.

figure 98.

The above figure represents only the upper part of the tube of the telescope, at which the observer stands when making his observations. The telescope is at present of the Newtonian construction, and consequently, the observer looks into the side of the tube at the upper end of the telescope, but it is proposed to throw aside the plane speculum, and to adapt it to theFront view, on the plan already described (see pp. 306, 313, &c.) so that the observer will sit or stand with his back towards the object, and his face looking down upon the speculum; and, in this position, he will sometimes be elevated between 50 and 60 feet above the ground. As yet, the telescope hasno equatorial motion, but it very shortly will; and at no very distant day, clock-work will be connected with it, when the observer will, while observing, be almost as comfortable, as if he were reading at a desk by his fire-side.

figure 99.

The following figure shews a section of the machinery connected with this telescope. It exhibits a view of the inside of the eastern wall, with all the machinery as seen in section. A is the mason-work on the ground, B the universal joint, which allows the tube to turn in all directions; C the speculum in its tube; D the box; E the eye-piece; F the moveable pulley; G the fixed one; H the chain from the side of the tube; I the chain from the beam; K the counterpoise; L the lever; M the chain connecting it with the tube; Z the chain which passes from the tube to the windlass over a pulley on a truss-beam which runs from W to the same situation on the opposite wall—the pulley is not seen. X is a railroad onwhich the speculum is drawn either to or from its box; part is cut away to show the counterpoise. The dotted linearepresents the course of the weight R as the tube rises or falls; it is a segment of a circle of which the chain I is the radius. The tube is moved from wall to wall by the ratchet and wheel at R; the wheel is turned by the handle O, and the ratchet is fixed to the circle on the wall. The ladders in front, as shown in the preceding sketch, enable the observer to follow the tube in its ascent to where the galleries on the side wall commence; these side galleries are three in number, and each can be moved from wall to wall by the observer, after the tube, the motion of which he also accomplishes by means of the handle O.

I shall conclude the description of this wonderful instrument in the words of Sir James South.

‘What will be the power of this telescope when it has its Le Mairean form’ [that is, when it is fitted up with the front view] ‘it is not easy to divine;—what nebulæ will it resolve into stars; in what nebulæ will it not find stars;—how many satellites of Saturn will it show us;—how many will it indicate as appertaining to Uranus;—how many nebulæ never yet seen by mortal eye, will it present to us;—what spots will it show us on the various planets; will it tell us what causes the variable brightness of many of the fixed stars;—will it give us any information as to the constitution of the planetary nebulæ;—will it exhibit to us any satellites encircling them; will it tell us why the satellites of Jupiter, which generally pass over Jupiter’s face as disks nearly of white light, sometimes traverse it as black patches;—will it add to our knowledge of the physical construction of nebulous stars;—of that mysterious class ofbodies which surround some stars, called, for want of a better name, ‘photospheres;’—will it show the annular nebulæ of Lyra, merely as a brilliant luminous ring, or will it exhibit it as thousands of stars arranged in all the symmetry of an ellipse; will it enable us to comprehend the hitherto incomprehensible nature and origin of the light of the great nebulæ of Orion;—will it give us, in easily appreciable quantity, the parallax of some of the fixed stars, or will it make sensible to us the parallax of the nebulae themselves;—finally, having presented to us original portraits of the moon and of the sidereal heavens, such as man has never dared even to anticipate—will it, by Daguerreotype aid, administer to us copies founded upon truth, and enable astronomers of future ages to compare the moon and heavens as they then may be, with the moon and heavens as they were? Some of these questions will be answered affirmatively, others negatively, and that, too, very shortly; for the noble maker of the noblest instrument ever formed by man, “has cast his bread upon the waters, and will, with God’s blessing, find it before many days.”’

As there are many among the lower ranks of the community who have a desire to be possessed of a telescope, which will show them some of the prominent features of celestial scenery, but who are unable to purchase a finished instrument at the prices usually charged by Opticians, the following hints may perhaps be acceptable to those who are possessed of a mechanical genius.

The lenses of an Achromatic telescope may be purchased separately from glass-grinders or Opticians, and tubes of a cheap material may be prepared by the individual himself for receiving the glasses. The following are the prices at which achromatic object-glasses for astronomical telescopes are generally sold. Focal length 30 inches, diameter 2¼ inches, from 2 to 3½ guineas. Focal length 42 inches, diameter 2¾ inches, from 5 to 8 guineas. Focal length 42 inches, diameter 3¼ inches, from 12 to 20 guineas. Focal length 42 inches, diameter 3¾ inches, from 25 to 30 guineas. Eye-pieces, from 10s. 6d. to 18 shillings. The smallest of these lenses, namely that of 2¼ inches diameter, if truly achromatic, may be made to bear a power of from 80 to 100 times, in clear weather, for celestial objects, which will show Jupiter’s moons and belts, Saturn’s ring and other celestial phenomena. The tubes may be made either of tin plates,papier maché, or wood. Wood, however, is rather a clumsy article, and it is sometimes liable to warp, yet excellent tubes have sometimes been made of it. Perhaps the cheapest and most convenient of all tubes whenproperly made, are those formed of paper. In forming these a wooden roller of the proper diameter should be procured, and paper of a proper size, along with book-binder’s paste. About three or four layers only of the paper should be pasted at one time, and, when sufficiently dry, it should be smoothed by rubbing it with a smooth stick or ruler; after which another series of layers should be pasted on, and allowed to dry as before, and so on till the tube has acquired a sufficient degree of strength and firmness. In this way, I have, by means of a few old Newspapers, and similar materials, formed tubes as strong as if they had been made of wood. If several tubes be intended to slide into each other, the smallest tube should be made first, and it will serve as a roller for forming the tube into which it is to slide.

An achromatic object glass of a shorter focal distance, and a smaller diameter than any of those stated above, may be fitted up as a useful astronomical telescope, when a better instrument cannot be procured. In the Pawn-broker’s shops in London, and other places, an old achromatic telescope, with an object-glass 20 inches focal distance and about 1½ inch diameter, may be purchased at a price varying from 15 to 20 shillings. By applying an astronomical eye-piece to such a lens, if a good one, it may bear a power, for celestial objects, of 50 or 60 times. If two plano-convex glasses, ¾ inch focal distance, be placed with their convex sides near to each other, they will form an eye-piece which will produce a power on such an object-glass, of above 50 times, which will show Jupiter’s belts and satellites, Saturn’s ring, the solar spots, and the mountains and cavities of the moon. I have an object-glass of this description which belonged to an old telescope,which cost me only 12 shillings, and with which I formerly made some useful astronomical observations. It was afterwards used as the telescope of a small Equatorial instrument, and, with it, I was enabled to perceive stars of the first and second magnitude, and the planets Venus, Jupiter, and Mars, inthe day-time.

But, should such a glass be still beyond the reach of the astronomical amateur, let him not altogether despair. He may purchase a single lens, 3 feet focal distance, for about a couple of shillings, and by applying an eye-glass of 1 inch focus, which may be procured for a shilling, he will obtain a power of 36 times, which is a higher power than Galileo was able to apply to his best telescope; and consequently, with such an instrument, he will be enabled to perceive all the celestial objects which that celebrated astronomer first described, and which excited so much wonder, at that period, in the learned world. But, whatever kind of telescope may be used, it is essentially requisite that it be placed on a firm stand in all celestial observations: and any common mechanic can easily form such a stand at a trifling expence.

There is a certain optical illusion to which most persons are subject, in the first use of telescopes, especially when applied to the celestial bodies, on which it may not be improper to make a remark. The illusion to which I allude is this—that they are apt to imagine, the telescope does not magnify nearly so much as it really does. They are apt to complain of the small appearance which Jupiter and Saturn, for example, present when magnified 160 or 200 times. With such powers they are apt to imagine, that these bodies do not appear so large as the moon to the naked eye. Yet it can be proved that Jupiter, when nearest the earth,viewed with such a power, appears about 5 times the diameter of the full moon, and 25 times larger in surface. This appears from the following calculation. Jupiter, when in opposition, or nearest the Earth, presents a diameter of 47´´: the mean apparent diameter of the moon is about 31´. Multiply the diameter of Jupiter by the magnifying power, 200, the product is 9400´´ or 156´ or 2° 36´, which, divided by 31´, the moon’s diameter, produces a quotient of 5, showing that this planet with such a power appears five times larger in diameter than the full moon to the naked eye, and consequently 25 times larger in surface. Were a power of only 50 times applied to Jupiter, when nearest the earth, that planet would appear somewhat larger than the full moon. For 47´´ multiplied by 50 gives 2350´´ or 39´, which is 8´ more than the diameter of the moon. Yet with such a power most persons would imagine that the planet does not appear one third of the size of the full moon.

The principal mode by which a person may be experimentally convinced of the fallacy to which I allude is the following:—At a time when Jupiter happens to be within a few degrees of the moon, let the planet be viewed through the telescope with the one eye, and the magnified image of the planet be brought into contact with the moon as seen with the other eye—the one eye looking at the moon, and the other viewing the magnified image of Jupiter through the telescope when brought into apparent contact with the moon—then it will be perceived, that with a magnifying power of 50 the image of Jupiter will completely cover the moon as seen by the naked eye;—and with a power of 200—when the moon is made to appear in the centre of the magnified image of theplanet—it will be seen that Jupiter forms a large and broad circle around the moon, appearing at least 5 times greater than the diameter of the moon. This experiment may be varied as follows: Suppose a person to view the moon through a small telescope or opera-glass, magnifying three times, he will be apt to imagine, at first sight, that she is not in the least magnified, but rather somewhat diminished. But let him bring the image as seen in the telescope in contact with the moon as seen with the naked eye, and he will plainly perceive the magnifying power, by the size of the image. It may be difficult in the first instance to look, at the same time, at the magnified image and the real object, but a few trials will render it easy.

THE END.

L. SEELEY PRINTER, THAMES DITTON.

Page 72 line 4 for EI, read FI.—— 103 — 30 — depend, read depends.—— 135 — 10 — refacting, read refracting.—— 136 — 10 — colour, read colours.—— 146 — 27 — G, read C.—— 146 — 32 — prisms, read prism.—— 153 — 35 — 28°3´, read 28° 10´—— 165 — 32 — some, read since.—— 165 — 33 dele that.—— 166 — 5 for these, read their.—— 166 — 21 — those, read their.—— 178 — 32 — variety, read vanity.—— 187 — 7 — in, read an.—— 187 — 11 — (p. 103.), read (p. 72.)—— 189 — 30 — lens, read lenses.—— 199 — 31 — punice, read pumice.—— 216 — 10 — nine, read ten.—— 236 — 12, 13 — “more distant from,” read “nearer to.”—— 337 — 27 — 1, read 1½.

FOOTNOTES:1Those unfortunate individuals who have been confined in the darkest dungeons have declared, that though on their first entrance, no object could be perceived, perhaps for a day or two, yet, in the course of time, as the pupils of their eyes expanded, they could readily perceive mice, rats, and other animals that infested their cells, and likewise the walls of their apartments; which shows that, even in such situations, light is present, and produces a certain degree of influence.2Letters to a German Princess, vol. l. pp. 68, 69, &c.3The manner in which the motion of light was discovered is explained in the author’s work, entitled ‘Celestial Scenery,’ pp. 369-371, and the circumstances which led to the discovery of the aberration of light are stated and illustrated in his volume on the ‘Sidereal Heavens,’ pp. 71-74, and pp. 284-292.4Nicolson’s Introduction to Natural Philosophy, vol. 1.5Light of a phosphoric nature, is frequently emitted from various putrescent animal substances which, in the ages of superstition, served to astonish and affright the timorous. We learn from Fabricius, an Italian, that three young men, residing at Padua, having bought a lamb, and eaten part of it on Easter Day, 1592, several pieces of the remainder which they kept till the following day, shone like so many candles when they were casually viewed in the dark. The astonishment of the whole city was excited by this phenomenon, and a part of the flesh was sent to Fabricius, who was Professor of anatomy, to be examined by him. He observed, that those parts which were soft to the touch and transparent in candle-light, were the most resplendent: and also that some pieces of kid’s flesh which had happened to have lain in contact with them were luminous, as well as the fingers and other parts of the bodies of those persons who touched them. Bartholin gives an account of a similar phenomenon, which happened at Montpelier in 1641. A poor woman had bought a piece of flesh in the market, intending to make use of it the following day, but happening not to be able to sleep well that night, and her bed and pantry being in the same room, she observed so much light come from the flesh as to illuminate all the place where it hung. We may judge of the terror and astonishment of the woman herself, when we find that a part of this luminous flesh was carried as a very extraordinary curiosity to Henry, Duke of Conde, the Governor of the place, who viewed it several hours with the greatest astonishment. The light was as if gems had been scattered over the surface, and continued till the flesh began to putrify, when it vanished, which it was believed to do in the form of a cross. Hence the propriety of instructing the mass of the community in the knowledge of the facts connected with the material system, and the physical causes of the various phenomena of nature.6Memoires de la Soc. d’Aroncil, vol. ii.7By amedium, in optics, is meant the space in which a ray of light moves, whether pure space, air, water, glass, diamond, or any other transparent substance through which the rays of light can pass in straight lines.8Edinburgh Philosophical Journal for October 1819, p. 411.9This mode of finding the focus of a concave lens may be varied as follows:—let the lens be covered with paper, having two small circular holes; and on the paper for receiving the light, describe also two small circles, but with their centres at twice the distance from each other of the centres of the circles. Then move the paper to and from, till the middle of the sun’s light, coming through the holes, falls exactly on the middle of the circles; that distance of the paper from the lens will be the focal length required.10Small glass mirrors for performing some of the experiments, and illustrating some of the principles above alluded to,—may be made of the flattest kind of common watch glasses, by foliating or covering with tin leaf and quicksilver the convex surfaces of such glasses. Their focal distances will generally be from one to two inches. Such mirrors afford a very large and beautiful view of the eye, when held within their focal distance of that organ. Such mirrors will also serve the purpose of reflecting light on the objects viewed by microscopes. Larger mirrors, of from four to eight inches diameter, may be had of the optician at different prices varying from five to ten or fifteen shillings.11Nicholson’s Journal of Natural Philosophy, &c. 4to. series, p. 225.12There can be little doubt that some of the facts ascribed, in the western highlands of Scotland, tosecond sight, have been owing to the unusual refraction of the atmosphere; as one of the peculiarities attributed to those who possessed this faculty was, that they were enabled to descry boats and snips, before they appeared in the horizon.13Fraunhofer was in the highest sense of the word, anOptician, an original discoverer in the most abstruse and delicate departments of this science—a competent mathematician, an admirable mechanist, and a man of a truly philosophical turn of mind. By his extraordinary talents, he was soon raised from the lowest station in a manufacturing establishment to the direction of theopticaldepartment of the business, in which he originally laboured as an ordinary workman. He then applied the whole power of his mind to the perfection of the achromatic telescope, the defects of which in reference to the optical properties of the materials used—he attempted to remedy; and by a series of admirable experiments, succeeded in giving to optical determinations, the precision of astronomical observations, surpassing, in this respect all who had gone before him, except perhaps, the illustrious Newton. It was in the course of these researches, that he was led to the important discovery of the dark lines which occur in the solar spectrum. His achromatic telescopes are scattered over Europe, and are the largest and best that have hitherto been constructed. He died at Munich, at a premature age, in 1826; his death, it is said being accelerated by the unwholesome nature of the processes employed in his glass-house; leaving behind him a reputation rarely attained by one so young. His Memoir “On the refractive and dispersive power of different species of glass, in reference to the improvement of Achromatic telescopes, and an account of the lines on the spectrum,” will be found in the “Edinburgh Philosophical Journal,” Vol. ix. pp. 288-299, and Vol. x. pp. 26-40, for 1823-4.14Philosophical Transactions. Vol. 50. p. 294.15Ecclesiasticus xliii. 11, 12.16It is a question which has been frequently started—Whether there was any rainbow before the flood? Some have conceived that the rainbow was something of amiraculousproduction, and that it was never seen before the flood. The equivocal sense of the word ‘set’ in our translation, has occasioned a mistaken impression of this kind. The Hebrew word thus translated, signifies more properly ‘I do give,’ or ‘Iappoint.’ The whole passage in reference to this circumstance, literally translated, runs thus;—“I appoint my bow which is in the cloud, that it may be for a sign or token of a covenant between me and the earth; and it shall come to pass when I bring a cloud over the earth, and the bow shall be seen in the cloud, that I will remember my covenant that is between me and you,” &c. As the rainbow is produced by the immutable laws of refraction and reflection, as applied to the rays of the sun striking on drops of falling rain, the phenomenon must have been occasionally exhibited from the beginning of the world: unless we suppose that there was no rain before the flood, and that the constitution of things in the physical system was very different from what it is now. The passage affirms no more than that the rainbow wasthen appointedto be asymbolof the covenant between God and man, and although it may have been frequently seen before, it would serve the purpose of a sign equally well, as if it had been miraculously formed for this purpose, and even better, as its frequent appearance, according to natural laws, is a perpetual memorial to man of the divine faithfulness and mercy.17Though Borellus mentions this circumstance, yet there is some reason to doubt the accuracy of this statement, as young Jansen appears to have been at that period, not more than six years old; so that it is more probable that Galileo was the first discoverer of Jupiter’s satellites.18The reader may see an engraving of this instrument in the author’s work entitled ‘theImprovement of Society.’—p. 209.19It is one of the properties of concave lenses to render convergent rays less convergent, and when placed as here supposed, to render them parallel; and it is parallel rays that produce distinct vision.20The wordapertureas applied to object-glasses, signifies the opening to let in the light, or that part of the object-glass which is left uncovered. An object-glass may be 3 inches in diameter, but if one inch of this diameter be covered, its aperture is said to be only 2 inches.21An achromatic telescope is said to be in possession of Mr. Cooper, M.P. for Sligo, which is 26 feet long, and the diameter of the object glass 14 inches.22This telescope, which was made by Dollond, with a power of 240 times, gives a beautiful view of the belts of Jupiter and the double ring of Saturn, and with a power of 50, the stars in the milky way and some of the nebulæ appear very numerous and brilliant. Its owner is a gentleman who unites science with Christianity.23For a more particular account of Dr. Blair’s instruments and experiments, the reader is referred to his Dissertation on this subject in Vol. II. of the ‘Transactions of the Royal Society of Edinburgh,’ which occupies 76 pages—or to Nicholson’s ‘Journal of Natural Philosophy,’ &c. Quarto Series, Vol. I., April, September, 1797.24A more detailed account of the processes connected with the construction of this telescope, will be found in a paper presented to the Royal Society, in 1827, and published in the Philosophical Transactions of that Society, for 1828, and likewise another paper, published in the Transactions for 1829. From these documents, chiefly, the preceding account has been abridged. See also the ‘Edinburgh New Philosophical Journal’ for Jan.,—April, 1828, and Brewster’s ‘Edinburgh Journal of Science,’ for October, 1829.25A particular description of this telescope, with the machinery for moving it, illustrated with an engraving, may be seen in Reid and Gray’s ‘Abridgement of the Philosophical Transactions.’—Vol. vi. Part I. for 1723, pp. 147-152.26Miss Short, who has erected and who superintends an observatory on the Calton hill, Edinburgh, is the descendant of a brother of Mr. Short. She is in possession of a large Gregorian reflector, about 12 feet long, made by Mr. Short, and mounted on an Equatorial axis. It was originally placed in a small observatory erected on the Calton hill, about the year 1776, but for many years past it has been little used.27A particular account of the Earl of Rosse’s fifty-feet Reflector, which is now finished, is given in theAppendix.28Philosophical Transactions for 1800, Vol. XC. p. 80, &c.29In using telescopes within doors, care should generally be taken, that there be no fires in the apartment where they are placed for observation, and that the air within be nearly of the same temperature as the air of the surrounding atmosphere; for if the room be filled with heated air, when the windows are opened, there will be a current of cold air rushing in, and of heated air rushing out, which will produce such an undulation and tremulous motion, as will prevent any celestial object from being distinctly seen.30The above directions and remarks are abridged with some alterations from Dr. Pearson’s “Introduction to Practical Astronomy.”—Vol. II.31Pearson’s “Practical Astronomy.”—Vol. II.32The mother-of-pearl dynameter may be purchased for about twelve shillings. See fig. 57,a,b,c, p. 260.33Reid’s Enquiry into the Human Mind, chap. iv.34The distance of Saturn from the sun is 906,000,000 of miles; it is sometimes nearer to and at other times farther from the earth, according as it is near the point of its opposition to, or conjunction with the sun. If this number be divided by 200, the supposed magnifying power of the telescope, the quotient is 4,530,000, which expresses the distance in miles at which it enables us to contemplate this planet. If this number be subtracted from 906,000,000, the remainder is 901,470,000, which expresses the number of miles from the earth at which we are supposed to view Saturn with such an instrument.35Irish Transactions, Vol. X. and Nicholson’s Philosophical Journal, Vol. XVI.36Brewster’s Appendix to ‘Ferguson’s Lectures.’37A particular description of the micrometers here enumerated, and several others, will be found in Dr. Pearson’s ‘Introduction to Practical Astronomy,’ Vol. II.38Adams’ Introduction to Practical Astronomy.39Or find the sun’s right ascension for the given day; substract this from the star or planet’s right ascension, and the remainder is the approximate time of the star’s coming to the meridian. The difference between this time and the time of observation, will then determine the point to which the telescope is to be directed.40The right ascensions, declinations, longitudes, &c., stated in these memoranda—which were noted at the time of observation—are only approximations to the truth; perfect accuracy in these respects being of no importance in such observations. They are, however, in general, within a minute or two of the truth. Thetimesof the observations, too, are noted in reference—not to theastronomical, but to thecivilday. The astronomical day commences at 12 noon, and the hours are reckoned, without interruption, to the following noon. The civil day commences at 12 midnight.41This observation is inserted in the ‘Edinburgh Philosophical Journal’ for January, 1844.42The late Mr. Benjamin Martin, when describing the nature of the solar telescope, in his ‘Philosophia Britannica,’ Vol. iii. p. 85, gives the following relation:—‘I cannot here omit to mention a veryunusual phenomenonthat I observed about ten years ago in my darkened room. The window looked towards the west, and the spire of Chichester Cathedral was before it at the distance of 50 or 60 yards. I used very often to divert myself by observing the pleasant manner in which the sun passed behind the spire, and was eclipsed by it for sometime; for the image of the sun and of the spire were very large, being made by a lens of 12 feet focal distance. And once as I observed the occultation of the sun behind the spire, just as the disk disappeared, I saw several small, bright, round bodies or balls running toward the sun from the dark part of the room, even to the distance of 20 inches. I observed their motion was a little irregular, but rectilinear, and seemed accelerated as they approached the sun. These luminous globules appeared also on the other side of the spire, and preceded the sun, running out into the dark room, sometimes more, sometimes less, together in the same manner as they followed the sun at its occultation. They appeared to be in general one-twentieth of an inch in diameter, and therefore, must be very large luminous globes in some part of the heavens, whose light was extinguished by that of the sun, so that they appeared not in open day light; but whether of the meteor kind, or what sort of bodies they might be, I could not conjecture.’ Professor Hansteen mentions, that when employed in measuring the zenith distances of the pole star, he observed a somewhat similar phenomenon, which he described as ‘a luminous body which passed over the field of the universal telescope—that its motion was neither perfectly equal nor rectilinear, but resembled very much the unequal and somewhat serpentine motion of an ascending rocket;’ and he concluded that it must have been ‘a meteor’ or ‘shooting star’ descending from the higher regions of the atmosphere.43In my frequent observations on Venus, to determine the nearest positions to the sun in which that planet could be seen, I had several times an opportunity of witnessing similar phenomena. I was not a little surprised, when searching for the planet, frequently to perceive a body pass across the field of the telescope, apparently of the same size as Venus, though sometimes larger and sometimes smaller, so that I frequently mistook that body for the planet, till its rapid motion undeceived me. In several instancesfourorfiveof these bodies appeared to cross the field of view, sometimes in a perpendicular, and, at other times in a horizontal direction. They appeared to be luminous bodies, somewhat resembling the appearance of a planet when viewed in the day-time with a moderate magnifying power. Their motion was nearly rectilinear, but sometimes inclined to a waving or serpentine form, and they appeared to move with considerable rapidity—the telescope being furnished with a power of about 70 times. I was for a considerable time at a loss what opinion to form of the nature of these bodies; but having occasion to continue these observations almost every clear day for nearly a twelvemonth, I had frequent opportunities of viewing this phenomenon in different aspects; and was at length enabled to form an opinion as to the cause of at leastsomeof the appearances which presented themselves. In several instances, the bodies alluded to appeared much larger than usual, and to move with a more rapid velocity; in which case I could plainly perceive that they were nothing else thanbirdsof different sizes, and apparently at different distances, the convex surfaces of whose bodies, in certain positions, strongly reflected the solar rays. In other instances, when they appeared smaller, their true shape was undistinguishable by reason of their motion and their distance.Having inserted a few remarks on this subject, in No. XXV. of the Edinburgh Philosophical Journal for July, 1825, particularly in reference to Professor Hansteen’s opinion, that article came under the review of M. Serres, Sub-Prefect of Embrun, in a paper inserted in theAnnales de Chemie, for October, 1825, entitled, ‘Notices regarding fiery meteors seen during the day.’44In the discussion of this subject, M. Serres admits that the light reflected very obliquely from the feathers of a bird is capable of producing an effect similar to that which I have now described; but that ‘the explanation ought not to begeneralized.’ He remarks, that, while observing the sun at the repeating circle, he frequently perceived, even through the coloured glass adapted to the eye-piece, large luminous points which traversed the field of the telescope, and which appeared too well defined not to admit them to be distant, and subtended too large angles to imagine them birds. In illustration of this subject he states the following facts. On the 7th September, 1820, after having observed for some time the eclipse of the sun which happened on that day, he intended to take a walk in the fields, and on crossing the town, he saw a numerous group of individuals of every age and sex, who had their eyes fixed in the direction of the sun. Further on, he perceived another group having their eyes in like manner turned towards the sun. He questioned an intelligent artist who was among them to learn the object that fixed his attention. He replied, ‘We are looking at the stars which are detaching themselves from the sun.’ ‘You may look yourself; that will be the shortest way to learn the fact.’ He looked, and saw, in fact, not stars, but balls of fire of a diameter equal to the largest stars, which were projected in various directions from the upper hemisphere of the sun, with an incalculable velocity, and although this velocity of projection appeared the same in all, yet they did not all attain the same distance. These globes were projected at unequal and pretty short intervals. Several were often projected at once, but always diverging from one another. Some of them described a right line, and were extinguished in the distance; some described a parabolic line, and were in like manner extinguished; others again, after having removed to a certain distance in a right line, retrograded upon the same line, and seemed to enter, still luminous, into the sun’s disk. The ground of this magnificent picture was a sky blue, somewhat tinged with brown. Such was his astonishment at the sight of so majestic a spectacle, that it was impossible for him to keep his eyes off it till it ceased, which happened gradually as the eclipse wore off and the solar rays resumed their ordinary lustre. It was remarked by one of the crowd that ‘the sun projected most stars at the time when it was palest;’ and that the circumstance which first excited attention to this phenomenon was that of a woman who cried out ‘Come here!—come and see the flames that are issuing from the sun!’I have stated the above facts because they may afterwards tend to throw light upon certain objects or phenomena with which we are at present unacquainted. The phenomenon of ‘falling stars’ has of late years excited considerable attention, and it seems now to be admitted, that, at least, certain species of these bodies descend from regions far beyond the limits of our atmosphere. This may be pronounced as certain with regard to the ‘November Meteors.’ May not some of the phenomena described above, be connected with the fall of meteoric stones—the showers of falling stars seen on the 12th and 13th of November, or other meteoric phenomena whose causes we have hitherto been unable to explain? Or, may we conceive that certain celestial bodies, with whose nature and destination we are as yet unacquainted, may be revolving in different courses in the regions around us—some of them opaque and others luminous, and whose light is undistinguishable by reason of the solar effulgence?43See Edinburgh Philosophical Journal, for April, 1825. No. XXIV.44See Edinburgh Philosophical Journal, for July, 1826, p. 114.45For an explanation of the manner of viewing Venus at her superior conjunction, see ‘Celestial Scenery,’ 5th thousand, p. 102.46See Long’s Astronomy, vol. 2, p. 487,—and Encyclopedia Britannica, vol. ii. p. 436, 3rd edition.47The balls which represent the different planets, on this machine, have their hemispheres painted black, with the white side turned directly to the sun, so that if the eye be placed in a line with the earth, and the planet, particularly Mercury and Venus, its phase in the heavens, at that time, as viewed with a telescope, may be distinctly perceived.48The above description has been selected and abridged from a small volume entitled ‘The Monster Telescope, erected by the Earl of Rosse, Parsontown,’—and also from the ‘Illustrated London News’ of September 9th, 1843. In the volume alluded to a more particular description will be found, accompanied with engravings.

1Those unfortunate individuals who have been confined in the darkest dungeons have declared, that though on their first entrance, no object could be perceived, perhaps for a day or two, yet, in the course of time, as the pupils of their eyes expanded, they could readily perceive mice, rats, and other animals that infested their cells, and likewise the walls of their apartments; which shows that, even in such situations, light is present, and produces a certain degree of influence.

2Letters to a German Princess, vol. l. pp. 68, 69, &c.

3The manner in which the motion of light was discovered is explained in the author’s work, entitled ‘Celestial Scenery,’ pp. 369-371, and the circumstances which led to the discovery of the aberration of light are stated and illustrated in his volume on the ‘Sidereal Heavens,’ pp. 71-74, and pp. 284-292.

4Nicolson’s Introduction to Natural Philosophy, vol. 1.

5Light of a phosphoric nature, is frequently emitted from various putrescent animal substances which, in the ages of superstition, served to astonish and affright the timorous. We learn from Fabricius, an Italian, that three young men, residing at Padua, having bought a lamb, and eaten part of it on Easter Day, 1592, several pieces of the remainder which they kept till the following day, shone like so many candles when they were casually viewed in the dark. The astonishment of the whole city was excited by this phenomenon, and a part of the flesh was sent to Fabricius, who was Professor of anatomy, to be examined by him. He observed, that those parts which were soft to the touch and transparent in candle-light, were the most resplendent: and also that some pieces of kid’s flesh which had happened to have lain in contact with them were luminous, as well as the fingers and other parts of the bodies of those persons who touched them. Bartholin gives an account of a similar phenomenon, which happened at Montpelier in 1641. A poor woman had bought a piece of flesh in the market, intending to make use of it the following day, but happening not to be able to sleep well that night, and her bed and pantry being in the same room, she observed so much light come from the flesh as to illuminate all the place where it hung. We may judge of the terror and astonishment of the woman herself, when we find that a part of this luminous flesh was carried as a very extraordinary curiosity to Henry, Duke of Conde, the Governor of the place, who viewed it several hours with the greatest astonishment. The light was as if gems had been scattered over the surface, and continued till the flesh began to putrify, when it vanished, which it was believed to do in the form of a cross. Hence the propriety of instructing the mass of the community in the knowledge of the facts connected with the material system, and the physical causes of the various phenomena of nature.

6Memoires de la Soc. d’Aroncil, vol. ii.

7By amedium, in optics, is meant the space in which a ray of light moves, whether pure space, air, water, glass, diamond, or any other transparent substance through which the rays of light can pass in straight lines.

8Edinburgh Philosophical Journal for October 1819, p. 411.

9This mode of finding the focus of a concave lens may be varied as follows:—let the lens be covered with paper, having two small circular holes; and on the paper for receiving the light, describe also two small circles, but with their centres at twice the distance from each other of the centres of the circles. Then move the paper to and from, till the middle of the sun’s light, coming through the holes, falls exactly on the middle of the circles; that distance of the paper from the lens will be the focal length required.

10Small glass mirrors for performing some of the experiments, and illustrating some of the principles above alluded to,—may be made of the flattest kind of common watch glasses, by foliating or covering with tin leaf and quicksilver the convex surfaces of such glasses. Their focal distances will generally be from one to two inches. Such mirrors afford a very large and beautiful view of the eye, when held within their focal distance of that organ. Such mirrors will also serve the purpose of reflecting light on the objects viewed by microscopes. Larger mirrors, of from four to eight inches diameter, may be had of the optician at different prices varying from five to ten or fifteen shillings.

11Nicholson’s Journal of Natural Philosophy, &c. 4to. series, p. 225.

12There can be little doubt that some of the facts ascribed, in the western highlands of Scotland, tosecond sight, have been owing to the unusual refraction of the atmosphere; as one of the peculiarities attributed to those who possessed this faculty was, that they were enabled to descry boats and snips, before they appeared in the horizon.

13Fraunhofer was in the highest sense of the word, anOptician, an original discoverer in the most abstruse and delicate departments of this science—a competent mathematician, an admirable mechanist, and a man of a truly philosophical turn of mind. By his extraordinary talents, he was soon raised from the lowest station in a manufacturing establishment to the direction of theopticaldepartment of the business, in which he originally laboured as an ordinary workman. He then applied the whole power of his mind to the perfection of the achromatic telescope, the defects of which in reference to the optical properties of the materials used—he attempted to remedy; and by a series of admirable experiments, succeeded in giving to optical determinations, the precision of astronomical observations, surpassing, in this respect all who had gone before him, except perhaps, the illustrious Newton. It was in the course of these researches, that he was led to the important discovery of the dark lines which occur in the solar spectrum. His achromatic telescopes are scattered over Europe, and are the largest and best that have hitherto been constructed. He died at Munich, at a premature age, in 1826; his death, it is said being accelerated by the unwholesome nature of the processes employed in his glass-house; leaving behind him a reputation rarely attained by one so young. His Memoir “On the refractive and dispersive power of different species of glass, in reference to the improvement of Achromatic telescopes, and an account of the lines on the spectrum,” will be found in the “Edinburgh Philosophical Journal,” Vol. ix. pp. 288-299, and Vol. x. pp. 26-40, for 1823-4.

14Philosophical Transactions. Vol. 50. p. 294.

15Ecclesiasticus xliii. 11, 12.

16It is a question which has been frequently started—Whether there was any rainbow before the flood? Some have conceived that the rainbow was something of amiraculousproduction, and that it was never seen before the flood. The equivocal sense of the word ‘set’ in our translation, has occasioned a mistaken impression of this kind. The Hebrew word thus translated, signifies more properly ‘I do give,’ or ‘Iappoint.’ The whole passage in reference to this circumstance, literally translated, runs thus;—“I appoint my bow which is in the cloud, that it may be for a sign or token of a covenant between me and the earth; and it shall come to pass when I bring a cloud over the earth, and the bow shall be seen in the cloud, that I will remember my covenant that is between me and you,” &c. As the rainbow is produced by the immutable laws of refraction and reflection, as applied to the rays of the sun striking on drops of falling rain, the phenomenon must have been occasionally exhibited from the beginning of the world: unless we suppose that there was no rain before the flood, and that the constitution of things in the physical system was very different from what it is now. The passage affirms no more than that the rainbow wasthen appointedto be asymbolof the covenant between God and man, and although it may have been frequently seen before, it would serve the purpose of a sign equally well, as if it had been miraculously formed for this purpose, and even better, as its frequent appearance, according to natural laws, is a perpetual memorial to man of the divine faithfulness and mercy.

17Though Borellus mentions this circumstance, yet there is some reason to doubt the accuracy of this statement, as young Jansen appears to have been at that period, not more than six years old; so that it is more probable that Galileo was the first discoverer of Jupiter’s satellites.

18The reader may see an engraving of this instrument in the author’s work entitled ‘theImprovement of Society.’—p. 209.

19It is one of the properties of concave lenses to render convergent rays less convergent, and when placed as here supposed, to render them parallel; and it is parallel rays that produce distinct vision.

20The wordapertureas applied to object-glasses, signifies the opening to let in the light, or that part of the object-glass which is left uncovered. An object-glass may be 3 inches in diameter, but if one inch of this diameter be covered, its aperture is said to be only 2 inches.

21An achromatic telescope is said to be in possession of Mr. Cooper, M.P. for Sligo, which is 26 feet long, and the diameter of the object glass 14 inches.

22This telescope, which was made by Dollond, with a power of 240 times, gives a beautiful view of the belts of Jupiter and the double ring of Saturn, and with a power of 50, the stars in the milky way and some of the nebulæ appear very numerous and brilliant. Its owner is a gentleman who unites science with Christianity.

23For a more particular account of Dr. Blair’s instruments and experiments, the reader is referred to his Dissertation on this subject in Vol. II. of the ‘Transactions of the Royal Society of Edinburgh,’ which occupies 76 pages—or to Nicholson’s ‘Journal of Natural Philosophy,’ &c. Quarto Series, Vol. I., April, September, 1797.

24A more detailed account of the processes connected with the construction of this telescope, will be found in a paper presented to the Royal Society, in 1827, and published in the Philosophical Transactions of that Society, for 1828, and likewise another paper, published in the Transactions for 1829. From these documents, chiefly, the preceding account has been abridged. See also the ‘Edinburgh New Philosophical Journal’ for Jan.,—April, 1828, and Brewster’s ‘Edinburgh Journal of Science,’ for October, 1829.

25A particular description of this telescope, with the machinery for moving it, illustrated with an engraving, may be seen in Reid and Gray’s ‘Abridgement of the Philosophical Transactions.’—Vol. vi. Part I. for 1723, pp. 147-152.

26Miss Short, who has erected and who superintends an observatory on the Calton hill, Edinburgh, is the descendant of a brother of Mr. Short. She is in possession of a large Gregorian reflector, about 12 feet long, made by Mr. Short, and mounted on an Equatorial axis. It was originally placed in a small observatory erected on the Calton hill, about the year 1776, but for many years past it has been little used.

27A particular account of the Earl of Rosse’s fifty-feet Reflector, which is now finished, is given in theAppendix.

28Philosophical Transactions for 1800, Vol. XC. p. 80, &c.

29In using telescopes within doors, care should generally be taken, that there be no fires in the apartment where they are placed for observation, and that the air within be nearly of the same temperature as the air of the surrounding atmosphere; for if the room be filled with heated air, when the windows are opened, there will be a current of cold air rushing in, and of heated air rushing out, which will produce such an undulation and tremulous motion, as will prevent any celestial object from being distinctly seen.

30The above directions and remarks are abridged with some alterations from Dr. Pearson’s “Introduction to Practical Astronomy.”—Vol. II.

31Pearson’s “Practical Astronomy.”—Vol. II.

32The mother-of-pearl dynameter may be purchased for about twelve shillings. See fig. 57,a,b,c, p. 260.

33Reid’s Enquiry into the Human Mind, chap. iv.

34The distance of Saturn from the sun is 906,000,000 of miles; it is sometimes nearer to and at other times farther from the earth, according as it is near the point of its opposition to, or conjunction with the sun. If this number be divided by 200, the supposed magnifying power of the telescope, the quotient is 4,530,000, which expresses the distance in miles at which it enables us to contemplate this planet. If this number be subtracted from 906,000,000, the remainder is 901,470,000, which expresses the number of miles from the earth at which we are supposed to view Saturn with such an instrument.

35Irish Transactions, Vol. X. and Nicholson’s Philosophical Journal, Vol. XVI.

36Brewster’s Appendix to ‘Ferguson’s Lectures.’

37A particular description of the micrometers here enumerated, and several others, will be found in Dr. Pearson’s ‘Introduction to Practical Astronomy,’ Vol. II.

38Adams’ Introduction to Practical Astronomy.

39Or find the sun’s right ascension for the given day; substract this from the star or planet’s right ascension, and the remainder is the approximate time of the star’s coming to the meridian. The difference between this time and the time of observation, will then determine the point to which the telescope is to be directed.

40The right ascensions, declinations, longitudes, &c., stated in these memoranda—which were noted at the time of observation—are only approximations to the truth; perfect accuracy in these respects being of no importance in such observations. They are, however, in general, within a minute or two of the truth. Thetimesof the observations, too, are noted in reference—not to theastronomical, but to thecivilday. The astronomical day commences at 12 noon, and the hours are reckoned, without interruption, to the following noon. The civil day commences at 12 midnight.

41This observation is inserted in the ‘Edinburgh Philosophical Journal’ for January, 1844.

42The late Mr. Benjamin Martin, when describing the nature of the solar telescope, in his ‘Philosophia Britannica,’ Vol. iii. p. 85, gives the following relation:—‘I cannot here omit to mention a veryunusual phenomenonthat I observed about ten years ago in my darkened room. The window looked towards the west, and the spire of Chichester Cathedral was before it at the distance of 50 or 60 yards. I used very often to divert myself by observing the pleasant manner in which the sun passed behind the spire, and was eclipsed by it for sometime; for the image of the sun and of the spire were very large, being made by a lens of 12 feet focal distance. And once as I observed the occultation of the sun behind the spire, just as the disk disappeared, I saw several small, bright, round bodies or balls running toward the sun from the dark part of the room, even to the distance of 20 inches. I observed their motion was a little irregular, but rectilinear, and seemed accelerated as they approached the sun. These luminous globules appeared also on the other side of the spire, and preceded the sun, running out into the dark room, sometimes more, sometimes less, together in the same manner as they followed the sun at its occultation. They appeared to be in general one-twentieth of an inch in diameter, and therefore, must be very large luminous globes in some part of the heavens, whose light was extinguished by that of the sun, so that they appeared not in open day light; but whether of the meteor kind, or what sort of bodies they might be, I could not conjecture.’ Professor Hansteen mentions, that when employed in measuring the zenith distances of the pole star, he observed a somewhat similar phenomenon, which he described as ‘a luminous body which passed over the field of the universal telescope—that its motion was neither perfectly equal nor rectilinear, but resembled very much the unequal and somewhat serpentine motion of an ascending rocket;’ and he concluded that it must have been ‘a meteor’ or ‘shooting star’ descending from the higher regions of the atmosphere.43In my frequent observations on Venus, to determine the nearest positions to the sun in which that planet could be seen, I had several times an opportunity of witnessing similar phenomena. I was not a little surprised, when searching for the planet, frequently to perceive a body pass across the field of the telescope, apparently of the same size as Venus, though sometimes larger and sometimes smaller, so that I frequently mistook that body for the planet, till its rapid motion undeceived me. In several instancesfourorfiveof these bodies appeared to cross the field of view, sometimes in a perpendicular, and, at other times in a horizontal direction. They appeared to be luminous bodies, somewhat resembling the appearance of a planet when viewed in the day-time with a moderate magnifying power. Their motion was nearly rectilinear, but sometimes inclined to a waving or serpentine form, and they appeared to move with considerable rapidity—the telescope being furnished with a power of about 70 times. I was for a considerable time at a loss what opinion to form of the nature of these bodies; but having occasion to continue these observations almost every clear day for nearly a twelvemonth, I had frequent opportunities of viewing this phenomenon in different aspects; and was at length enabled to form an opinion as to the cause of at leastsomeof the appearances which presented themselves. In several instances, the bodies alluded to appeared much larger than usual, and to move with a more rapid velocity; in which case I could plainly perceive that they were nothing else thanbirdsof different sizes, and apparently at different distances, the convex surfaces of whose bodies, in certain positions, strongly reflected the solar rays. In other instances, when they appeared smaller, their true shape was undistinguishable by reason of their motion and their distance.Having inserted a few remarks on this subject, in No. XXV. of the Edinburgh Philosophical Journal for July, 1825, particularly in reference to Professor Hansteen’s opinion, that article came under the review of M. Serres, Sub-Prefect of Embrun, in a paper inserted in theAnnales de Chemie, for October, 1825, entitled, ‘Notices regarding fiery meteors seen during the day.’44In the discussion of this subject, M. Serres admits that the light reflected very obliquely from the feathers of a bird is capable of producing an effect similar to that which I have now described; but that ‘the explanation ought not to begeneralized.’ He remarks, that, while observing the sun at the repeating circle, he frequently perceived, even through the coloured glass adapted to the eye-piece, large luminous points which traversed the field of the telescope, and which appeared too well defined not to admit them to be distant, and subtended too large angles to imagine them birds. In illustration of this subject he states the following facts. On the 7th September, 1820, after having observed for some time the eclipse of the sun which happened on that day, he intended to take a walk in the fields, and on crossing the town, he saw a numerous group of individuals of every age and sex, who had their eyes fixed in the direction of the sun. Further on, he perceived another group having their eyes in like manner turned towards the sun. He questioned an intelligent artist who was among them to learn the object that fixed his attention. He replied, ‘We are looking at the stars which are detaching themselves from the sun.’ ‘You may look yourself; that will be the shortest way to learn the fact.’ He looked, and saw, in fact, not stars, but balls of fire of a diameter equal to the largest stars, which were projected in various directions from the upper hemisphere of the sun, with an incalculable velocity, and although this velocity of projection appeared the same in all, yet they did not all attain the same distance. These globes were projected at unequal and pretty short intervals. Several were often projected at once, but always diverging from one another. Some of them described a right line, and were extinguished in the distance; some described a parabolic line, and were in like manner extinguished; others again, after having removed to a certain distance in a right line, retrograded upon the same line, and seemed to enter, still luminous, into the sun’s disk. The ground of this magnificent picture was a sky blue, somewhat tinged with brown. Such was his astonishment at the sight of so majestic a spectacle, that it was impossible for him to keep his eyes off it till it ceased, which happened gradually as the eclipse wore off and the solar rays resumed their ordinary lustre. It was remarked by one of the crowd that ‘the sun projected most stars at the time when it was palest;’ and that the circumstance which first excited attention to this phenomenon was that of a woman who cried out ‘Come here!—come and see the flames that are issuing from the sun!’I have stated the above facts because they may afterwards tend to throw light upon certain objects or phenomena with which we are at present unacquainted. The phenomenon of ‘falling stars’ has of late years excited considerable attention, and it seems now to be admitted, that, at least, certain species of these bodies descend from regions far beyond the limits of our atmosphere. This may be pronounced as certain with regard to the ‘November Meteors.’ May not some of the phenomena described above, be connected with the fall of meteoric stones—the showers of falling stars seen on the 12th and 13th of November, or other meteoric phenomena whose causes we have hitherto been unable to explain? Or, may we conceive that certain celestial bodies, with whose nature and destination we are as yet unacquainted, may be revolving in different courses in the regions around us—some of them opaque and others luminous, and whose light is undistinguishable by reason of the solar effulgence?

In my frequent observations on Venus, to determine the nearest positions to the sun in which that planet could be seen, I had several times an opportunity of witnessing similar phenomena. I was not a little surprised, when searching for the planet, frequently to perceive a body pass across the field of the telescope, apparently of the same size as Venus, though sometimes larger and sometimes smaller, so that I frequently mistook that body for the planet, till its rapid motion undeceived me. In several instancesfourorfiveof these bodies appeared to cross the field of view, sometimes in a perpendicular, and, at other times in a horizontal direction. They appeared to be luminous bodies, somewhat resembling the appearance of a planet when viewed in the day-time with a moderate magnifying power. Their motion was nearly rectilinear, but sometimes inclined to a waving or serpentine form, and they appeared to move with considerable rapidity—the telescope being furnished with a power of about 70 times. I was for a considerable time at a loss what opinion to form of the nature of these bodies; but having occasion to continue these observations almost every clear day for nearly a twelvemonth, I had frequent opportunities of viewing this phenomenon in different aspects; and was at length enabled to form an opinion as to the cause of at leastsomeof the appearances which presented themselves. In several instances, the bodies alluded to appeared much larger than usual, and to move with a more rapid velocity; in which case I could plainly perceive that they were nothing else thanbirdsof different sizes, and apparently at different distances, the convex surfaces of whose bodies, in certain positions, strongly reflected the solar rays. In other instances, when they appeared smaller, their true shape was undistinguishable by reason of their motion and their distance.

Having inserted a few remarks on this subject, in No. XXV. of the Edinburgh Philosophical Journal for July, 1825, particularly in reference to Professor Hansteen’s opinion, that article came under the review of M. Serres, Sub-Prefect of Embrun, in a paper inserted in theAnnales de Chemie, for October, 1825, entitled, ‘Notices regarding fiery meteors seen during the day.’44In the discussion of this subject, M. Serres admits that the light reflected very obliquely from the feathers of a bird is capable of producing an effect similar to that which I have now described; but that ‘the explanation ought not to begeneralized.’ He remarks, that, while observing the sun at the repeating circle, he frequently perceived, even through the coloured glass adapted to the eye-piece, large luminous points which traversed the field of the telescope, and which appeared too well defined not to admit them to be distant, and subtended too large angles to imagine them birds. In illustration of this subject he states the following facts. On the 7th September, 1820, after having observed for some time the eclipse of the sun which happened on that day, he intended to take a walk in the fields, and on crossing the town, he saw a numerous group of individuals of every age and sex, who had their eyes fixed in the direction of the sun. Further on, he perceived another group having their eyes in like manner turned towards the sun. He questioned an intelligent artist who was among them to learn the object that fixed his attention. He replied, ‘We are looking at the stars which are detaching themselves from the sun.’ ‘You may look yourself; that will be the shortest way to learn the fact.’ He looked, and saw, in fact, not stars, but balls of fire of a diameter equal to the largest stars, which were projected in various directions from the upper hemisphere of the sun, with an incalculable velocity, and although this velocity of projection appeared the same in all, yet they did not all attain the same distance. These globes were projected at unequal and pretty short intervals. Several were often projected at once, but always diverging from one another. Some of them described a right line, and were extinguished in the distance; some described a parabolic line, and were in like manner extinguished; others again, after having removed to a certain distance in a right line, retrograded upon the same line, and seemed to enter, still luminous, into the sun’s disk. The ground of this magnificent picture was a sky blue, somewhat tinged with brown. Such was his astonishment at the sight of so majestic a spectacle, that it was impossible for him to keep his eyes off it till it ceased, which happened gradually as the eclipse wore off and the solar rays resumed their ordinary lustre. It was remarked by one of the crowd that ‘the sun projected most stars at the time when it was palest;’ and that the circumstance which first excited attention to this phenomenon was that of a woman who cried out ‘Come here!—come and see the flames that are issuing from the sun!’

I have stated the above facts because they may afterwards tend to throw light upon certain objects or phenomena with which we are at present unacquainted. The phenomenon of ‘falling stars’ has of late years excited considerable attention, and it seems now to be admitted, that, at least, certain species of these bodies descend from regions far beyond the limits of our atmosphere. This may be pronounced as certain with regard to the ‘November Meteors.’ May not some of the phenomena described above, be connected with the fall of meteoric stones—the showers of falling stars seen on the 12th and 13th of November, or other meteoric phenomena whose causes we have hitherto been unable to explain? Or, may we conceive that certain celestial bodies, with whose nature and destination we are as yet unacquainted, may be revolving in different courses in the regions around us—some of them opaque and others luminous, and whose light is undistinguishable by reason of the solar effulgence?

43See Edinburgh Philosophical Journal, for April, 1825. No. XXIV.

44See Edinburgh Philosophical Journal, for July, 1826, p. 114.

45For an explanation of the manner of viewing Venus at her superior conjunction, see ‘Celestial Scenery,’ 5th thousand, p. 102.

46See Long’s Astronomy, vol. 2, p. 487,—and Encyclopedia Britannica, vol. ii. p. 436, 3rd edition.

47The balls which represent the different planets, on this machine, have their hemispheres painted black, with the white side turned directly to the sun, so that if the eye be placed in a line with the earth, and the planet, particularly Mercury and Venus, its phase in the heavens, at that time, as viewed with a telescope, may be distinctly perceived.

48The above description has been selected and abridged from a small volume entitled ‘The Monster Telescope, erected by the Earl of Rosse, Parsontown,’—and also from the ‘Illustrated London News’ of September 9th, 1843. In the volume alluded to a more particular description will be found, accompanied with engravings.

Transcriber’s Note:The corrections listed in the Errata list have been made.The high resolution image for the image on page 196 does not have a caption. I have captioned this image as "figure 40" and the one on page 206 as "figure 40*" to comply with the "List of Engravings".Inconsistent double quotes and capitalization are as in the original.Inconsistent spelling and hyphenation are as in the original.

The corrections listed in the Errata list have been made.

The high resolution image for the image on page 196 does not have a caption. I have captioned this image as "figure 40" and the one on page 206 as "figure 40*" to comply with the "List of Engravings".

Inconsistent double quotes and capitalization are as in the original.

Inconsistent spelling and hyphenation are as in the original.

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