236 



Dr. Miiller on the Thermal Effects 



either successively (in position) or side by side. The latter 

 arrangement was found to cause a deflection more than twice as 

 great as that caused by the former for equal radiations upon the 

 thermo-battery. Hence in the following experiments the latter 

 (side by side) aiTangement was always adopted. Such a com- 

 bination represents in reality a parcel of 925 convolutions of 

 wire four times as thick as the single wire (OS millim. diameter). 

 This multiplier was placed upon a bracket near the window of a 

 neighbouring room. The current was conveyed from the thermo- 

 battery to the multiplier and back through a 1 millim. thick 

 copper wire covered with spun wool. 



Before performing the separate series of experiments, this 

 multiplier was graduated according to Melloni's method. Call- 

 ing the strength of the current 1 which causes a deflection of 1° 

 in the instrument, it was found that the deflection I'emained 

 proportional to the strength of the current up to 20° ; beyond 

 this point, however, the following corresponding relations were 

 found to exist between the deflection and the strength of the 

 current. 



In the experiments upon the thermal rays which are trans- 

 mitted through coloui'ed liquids, I made use of the thermo- 

 battery already mentioned, consisting of forty bismuth-antimony 

 couples. I am unable to give the origin of this battery, it 

 having been in the Freiburg Physical Cabinet for a long time. 

 For the experiments concerning the disti'ibution of heat in the 

 spectrum itself, I employed a lineal thermo-battery of fifteen 

 couples especially procured for this purpose*. Masson and 

 Jamin made use of a thermo-battery of exactly the same con- 

 struction in their experiments on the heat of the solar spec- 

 trum. 



* Procured from Lcrebours et Secretan, Paris. See their Catalogue, 

 No. 765. p. 93. 



