( 131 ) 



On the Refraction and Polarization of Heat. By James D. Forbes, 

 Esq., F. R. SS. L. & E., Professor of Natural Philosophy in the 

 University of Edinburgh. 



[Read 5th and 19th January 1835.) 



§ 1, Some Miscellaneous Experiments with the Thermo- Multi- 

 plier. § 2. On the Polarization of Heat by Tourmaline. 

 § S. On the Polarization of Heat by Refraction and Re- 

 fection. § 4. On the Depolarization and Double Refrac- 

 tion of Heat. 



1. The experiments to be detailed in this paper, which chief- 

 ly go to establish properties of heat wholly unlooked for, or only 

 suspected to exist, having been made entirely by means of an in- 

 strument of great delicacy — the thermo-multiplier of MM. No- 

 bili and Melloni, I shall premise some account of its application 

 to the investigation of some more familiar modes of action. 



§ 1. Miscellaneous Experiments. 



2. We could hardly quote a stronger proof of the rapid and 

 unexpected advances which enlarged theory may produce in 

 practice, than by referring to the employment of thermo-electric 

 action, discovered a few years since by Seebeck, to the mea- 

 surement of heat, with a degree of accuracy and facility which, 

 perhaps, no thermometer has ever attained. Such is the prin- 

 ciple of the thermo-multiplier of Nobili and Melloni. It is well 

 known, that when two metals (and especially bismuth and anti- 

 mony) are soldered together, and the point of union heated, an 

 electric current is established from the one metal to the other, 



r 2 



