569 



and at temperature 26 Cent., the heating effect of ten atmospheres 

 is found to be ~ of a degree Cent. 



TABLE giving the thermal effects of a pressure of ten atmospheres 

 on water and mercury*. 



XXIII. " On the Phenomenon of Relief of the Image formed 

 on the Ground Glass of the Camera Obscura." By A. 

 CLAUDET, Esq., F.R.S. Received June 17, 1857. 

 (Abstract.) 



The author having observed that the image formed on the 

 ground glass of the camera obscura appears as much in relief as 

 the natural object when seen with the two eyes, has endeavoured 

 to discover the cause of that phenomenon, and his experiments and 

 researches have disclosed the singular and unexpected fact, that 

 although only one image seems depicted on the ground glass, still 

 each eye perceives a different image ; that in reality there exist on 

 the ground glass two images, the one visible only to the right eye, 

 and the other visible only to the left eye. That the image seen by 

 the right eye is the representation of the object refracted by the left 

 side of the lens, and the image seen by the left eye is the represen- 

 tation of the object refracted by the right side of the lens. Con- 

 sequently these two images presenting two different perspectives, the 

 * Added August 1. 



