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XXI. Researches on Heat. Second Series

Published online by Cambridge University Press:  17 January 2013

James D. Forbes Esq.
James D. Forbes Esq.
Affiliation:
Professor of Natural Philosophy in theUniversity of Edinburgh.
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Extract

1. The first series of these researches, in the exact form in which they are printed, were laid before the Royal Society on the 19th January 1835. The whole of the experiments there described were made, and the paper written and printed, within a space of time little exceeding two months. This haste, unfavourable to composition, I considered as a less evil than postponing for a period of time, which must have been considerable, the publication of a class of facts which might be said almost to embrace a new science. The professional duties which pressed upon me during the whole continuance of those experiments, then called imperatively on my attention, and during the remainder of the Session my time was devoted to them. The summer I devoted to a foreign excursion, some of the results of which I afterwards digested; and it was not till the commencement of the winter session which has just closed, that I prepared, with a fresh stock of health and spirits, to reinvestigate the whole subject of the Polarization of Heat, and to assign numerical values to the effects, whose existence I had before been contented to prove.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 13 , Issue 2 , 1836 , pp. 446 - 471
Copyright
Copyright © Royal Society of Edinburgh 1836

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References

page 448 note * References to Fig. 1.—P, the thermal pile. KI, LH, the wires conveying the electricity from the pile to the galvanometer, G, the galvanometer card, over which the needle traverses. EF, the cover of the galvanometer, which has a plane glass top. BC, a telescope, with a diagonal eye-piece, having an additional objectglass at D, in order to give distinct vision of the galvanometer-needle and the scale (see First Series, art. 5). A, the telescope-bearer, moving round a point concentric with G M, the trumpet-mouthed reflector, applied to the pile (art. 6, below).

page 449 note * Suppose that we wish to have a conical reflector ABCD, such that the whole of the parallel rays which fall upon it shall reach some part of the surface AB of the pile, which is all that we want, we have this simple construction. Let the length of the trumpet-mouth AE be given. Make FB equal and parallel to it. Join FA, and prolong the line to D, then is DAE the greatest inclination that the sides of the cone can have to answer the purpose intended.

page 356 note * Philosophical Magazine and Annals, for November 1835 and March 1836.

page 361 note * For a supply of this valuable substance I have been greatly indebted both to Sir Philip Grey Egerton, Baronet, of Oulton Park, Cheshire, and to Dr Traill.

page 361 note † Such plates being equally permeable to every kind of heat, as M. Melloni's admirable experiment shews, would probably enable us to polarize cold, or to shew the negative effects due to a reduction of temperature. This experiment I have not tried.

page 363 note * Edinburgh Journal of Science, N. S., vols. iii. and v.

page 363 note † Bibliotheque Universelle, Sept 1834.

page 364 note * Square tubes of wood, seen distinctly in the perspective view, serve to enclose the apparatus and facilitate its adjustment. Other means not represented in the figure were also used for preventing direct heat from reaching the pile in any position.

page 466 note * Probably owing to its still more heterogeneous character.

page 469 note * Only 50 per cent. of the heat was polarized instead of 63, as in the Table (art 22). The reason is, that the mica bundle M, used on this occasion, polarized less completely than that marked K. I have invariably found the per-centage of heat polarized after total reflection within rock-salt, in, or perpendicular to, the plane of primitive polarization, to agree most closely with the results obtained when no reflection had taken place.

page 471 note * Philosophical Transactions, 1830.