Journal of Applied Microscopy. 



95 



Fig. 2. 



horizontal position, and folding down 

 parallel with the bellows so as to be out 

 of the way when in any other position. 

 The vertical rods are graduated in inches 

 for determining the amount of ampli- 

 fication and to show when the ground 

 glass is at right angles to the optical 

 axis. The following simple rule for de- 

 termining the amount of amplification, 

 will give sufficiently accurate results. 

 When photographing without the eye- 

 piece, divide the distance of the ground 

 glass from the stage of the micro- 

 scope in inches by the focal length in 

 inches of the objective used. When pho- 

 tographing with the eyepiece, proceed as 

 above and multiply the quotient obtained 

 by the quotient obtained by dividing 10 

 by the focus in inches of the eyepiece 

 used. 



A valuable feature of this camera is 

 that the microscope can be placed in any 

 position desired and the camera adjusted 

 to it. The bellows can then be raised and 

 the microscope used as though no camera 

 were present. When an object is to be 

 photographed, the bellows may be slid 

 into position without in any way dis- 

 turbing the arrangement of light or ob- 

 ject, the final focusing on the ground 

 glass being effected quickly by means of 

 the fine adjustment screw. The expos- 

 ure having been made, observation 

 through the microscope may be con- 

 tinued without interruption by simply 

 raising the bellows again. The use of 

 the two supporting rods for the camera 



gives the necessary steadiness to the 

 sensitive plate during exposure which it 

 is very difficult to obtain in the vertical 

 or inclinable camera in any other way. 



Figure 1 shows the camera in the in- 

 clined position; figure 2, as it would be 

 used horizontal. 



H. Bausch. 



Rochester, N. T. 



ABSTRACTS. 



Copper Crystals in Adventurine Glass.* 



The material is known to the jewelry 

 trade as "gold stone." Mr. James 

 Walker, of the Brooklyn Institute, 

 informs me that an English work gives 

 oxide of copper as the compound used 

 in its manufacture. 



One of the most curious products of 

 the world-renowned glass works at 

 Murano, near Venice, is the so-called 

 "adventurine glass" (vetro adventurino), 

 which owes its name, according to the 

 story, to its discovery by chance (all' 

 av Ventura), some brass filmgs having 

 been dropped accidentally into a pot of 

 molten glass. 



The glass is of a copper brown color, 

 and transparent to translucent, in thin 

 flakes, showing on the edges a pale 

 brown color. It is filled with innumer- 



* From American Journal of Science, Nov., 1894, 

 by Henry S. Washington, Venice, Italy. 



