LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



SUPPLEMENT to VOL. XIL, THIRD SERIES. 



LXXXII. Researches on Heat, Second Series, By James D. 

 Forbes, Esq., F.KSS. L. ^ E., Professor of Natural Phi- 

 losojphy in the University of Edinburgh,^ 



§ 1, On the Use of the Thermo- Multiplier, § 2. On the Polar- 

 ization of Heat by Tourmaline, \ 3. On the Laws of the 

 Polarization of Heat by Refraction, § 4. On the Laws of 

 the Polarization of Heat by Reflection, § 5. On the Circu- 

 lar Polarization of Heat, 



'T^HE first series of these researches, in the exact form in 

 which they are printed, were laid before the Royal So- 

 ciety on the 19th January 1835 f. 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 atten-' 

 tion, and during the remainder of the Session my time was 

 devoted to them. The summer I devoted to a foreign excur- 

 sion, some of the results of which I afterwards digested ; and 

 it was not till the commencement of the winter session which 

 has just closedj that I prepared, with a fresh stock of health 

 and spirits, to reinvestigate the whole subject of the Polari- 

 zation of Heat, and to assign numerical values to the effects, 

 whose existence I had before been contented to prove. 



§ 1. On the Use of the Thermo- Multiplier, 

 I have succeeded in rendering the application of the 

 thermo-multiplier considerably easier, and more delicate 

 than formerly. In my last paper, art. 5, I described 

 the application of the telescope to determine accurately the 

 amount of the deviation of the needle of the instrument in- 

 dicating degrees of temperature. I have made the arrange- 

 ment more permanent, placing the instrument on one shelf 



* Abridged by the Author from the Transactions of the Royal Society, 

 vol. xiii., having been read before the Society May 2nd, 1836. 



f [Prof. Forbes's First Series of Researches on Heat appeared in Lond, 

 and Edinb. Phil. Mag., vol. vi. p. 134 et seq.'] 

 Phil. Mag, S. 3. Vol. 12. No. 78. Suppl, July 1838. 2 Y 



