1 Those 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.

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

3 The 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.

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

5 Light 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.

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

7 By a medium, 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.

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

9 This 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.

10 Small 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.

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

12 There can be little doubt that some of the facts ascribed, in the western highlands of Scotland, to second 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.

13 Fraunhofer was in the highest sense of the word, an Optician, 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 the optical department 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.

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

15 Ecclesiasticus xliii. 11, 12.

16 It 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 a miraculous production, 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 ‘I appoint.’ 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 was then appointed to be a symbol of 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.

17 Though 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.

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

19 It 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.

20 The word aperture as 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.

21 An 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.

22 This 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.

23 For 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.

24 A 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.

25 A 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.

26 Miss 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.

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

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

29 In 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.

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

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

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

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

34 The 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.

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

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

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

38 Adams’ Introduction to Practical Astronomy.

39 Or 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.

40 The 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. The times of the observations, too, are noted in reference—not to the astronomical, but to the civil day. 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.

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

42 The 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 very unusual phenomenon that 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.43

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 instances four or five of 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 least some of 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 than birds of 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 the Annales de Chemie, for October, 1825, entitled, ‘Notices regarding fiery meteors seen during the day.’44 In 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 be generalized.’ 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?

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

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

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

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

47 The 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.

48 The 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.