[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.