and the Mode of its Communication 123 



The surface of the cold disk A having been black- 

 ened as well as that of the hot disk B, when both disks 

 (blackened) were again presented at equal distances to 

 the ball of the thermoscope, as represented in Fig. 6, it 

 was found that the original temperature of the thermo- 

 scope remained unchanged. 



The result of this most interesting experiment proves 

 that the ball of the thermoscope was just as much 

 cooled by the influence of the cold blackened disk as it 

 was heated by the hot blackened disk. 



Now, as it was found by experiment that the intensity 

 of the radiation of the disk B was increased by the black- 

 ening of the surface of that disk, we must conclude 

 that the intensity of the radiation of the disk A was 

 likewise increased by the use of the same means ; but if 

 those radiations be caloric^ emitted by those bodies 

 (which the hypothesis in question supposes), how did it 

 happen that the ball of the thermoscope, instead of being 

 more heated by the additional quantity of caloric which 

 it received in consequence of the blackening of the disk 

 A, was actually more cooled? 



It may perhaps be said by the advocates for the hy- 

 pothesis in question, that the blackening of the surface 

 of the disk A caused a greater quantity of caloric to be 

 sent off to it by the ball of the thermoscope. Without 

 insisting on an explanation of the mode of action of the 

 cause which is supposed to produce this effect (which I 

 might certainly do, as the supposition is perfectly gra- 

 tuitous), I will content myself with just observing that 

 as the surface of the opposite disk was also blackened^ 

 this supposed augmentation of the quantity of caloric 

 emitted by the ball of the thermoscope, occasioned by 

 the blackening of the surfaces of the bodies -presented to if, 



