London: LONGMANS, GREEN, & CO.
FOOTNOTES:
[1] Other green lines have since been discovered in the auroral spectrum; and occasionally a red line is seen.
[2] In the Quarterly Journal of Science for October 1866, a more detailed but somewhat less popular account of the subject of the above paper is presented. A few months earlier, a skilfully-written paper on the same subject, from the pen of Mr. J. M. Wilson, of Rugby, had appeared in the Eagle, a magazine written by and for
members of St. John’s College, Cambridge. Although my paper in
the Quarterly Journal of Science was written quite independently of Mr. Wilson’s (which, however, I had read), yet it chanced that in describing the same mathematical relations, and the same sequence of events, I here and there used language closely resembling his. I fear this led for a while to some misconception; but I was fortunately able to show in Mr. De la Rue’s address to the Astronomical Society, on the same subject, passages yet more strikingly resembling some in Mr. Wilson’s paper (written subsequently and quite independently). The fact would seem to be that if two persons describe exactly the same events, and deal with exactly the same mathematical relations, it is almost certain that in more than one passage they will use somewhat similar expressions.
I was actually indebted to Mr. Wilson’s paper for one illustration, however,—that derived from the movements of a supposed artificial moon; and I think that had his paper appeared in a magazine printed for general circulation, I should have referred to it. As it was, this seemed useless so far as the readers of the Quarterly Journal of Science were concerned. The circumstances of the case were, indeed, far from calling for a reference; while I had in a sense made the illustration my own by detecting an important miscalculation in the original (the amount of advance being either doubled or halved—I forget which). Had I referred to Mr. Wilson’s paper, I must needs have mentioned this mistake; and it would have appeared as though I had had no other purpose in making the reference.
I mention these matters to explain what I fear my esteemed fellow-collegian was disposed at the time to regard as either a wrong or a slight. Nothing was further from my intention than either.
[3] The reader will remember the time at which the essay appeared. For several reasons it seems well to leave the essay unaltered. In the second series of Light Science a later stage is presented, and the account is carried up to the present date in my work on The Transits of Venus.
[4] It is held to be of the utmost importance that all the observing parties should use similar telescopes.
[5] So far back as 1789, John Williams, in his Natural History of the Mineral Kingdom, discussed the question of the ‘Limited Quantity of Coal in Great Britain.’ The following extracts are taken from an excellent paper on the exhaustion of our coal in the Popular Science Review for July 1866, by Mr. Lemoran, Colliery Viewer. ‘I have no doubt,’ says Williams, ‘that the generality of the inhabitants of Great Britain believe that our coal mines are inexhaustible; and the general conduct of the nation, so far as relates to this subject, seems to imply that this is held as an established fact. If it was not a generally received opinion, would the rage for exporting coals be allowed to go on without limitation or remorse? But it is full time that the public were undeceived in a matter which so nearly concerns the welfare of this flourishing island.... When our coal mines are exhausted, the prosperity and glory of this flourishing and fortunate island are at an end. Our cities and great towns must then become ruinous heaps for want of fuel, and our mines and manufactories must fail from the same cause, and then, consequently, our commerce must vanish. In short, the commerce, wealth, importance, glory, and happiness of Great Britain will decay and gradually dwindle away to nothing, in proportion as our coal and other mines fail.’ Mr. Williams also solves in a very summary manner the problem of England’s fate after her coal stores shall be exhausted. ‘The future inhabitants of this island must live,’ says he, ‘like its first inhabitants, by fishing and hunting.’