W, HISLOP ON A NEW ANALYZING 8ELENITB STAGE. 



229 



revolve tliree toothed rings, forming three separate cells. The 

 lower one has a projecting flange on the lower side, which revolves 

 in the lower orifice. The centre ring has also a flange, which turns 

 in a recess in the lower ring, and the upper one is kept in place in 

 a similar manner. From the right edge of the plates project two 

 discs with milled edges, which are each divided into eight parts, 

 numbered alternately 1 to 4. On the left edge there is a similar 

 disc. 



Fig 2. 



Fig 3. 



Each of the toothed rings in the centre is connected with 

 a small toothed wheel on the under side of each of these 

 discs, by other toothed wheels, so that when either disc is 

 turned its corresponding ring also revolves. The selenites 



