430 



A. E. SMITH OX STEREO-PHOTO-MICROGRAPHY. 



pierced in it, and when the image is focussed, put this stop 

 in front of the lens and move the stop about. The image will 

 change with every movement of the stop. 



It will now be understood how easy it is to get only two 

 different images through the microscope with the excentric stop. 



A second method of obtaining stereoscopic photographs of 



Kior 2 



microscopic objects is by tilting the object first one way and 

 then the other, and securing a negative in each position. This 

 is suitable for low powers only. 



A third method is by moving the object a short distance across 

 the stage and securing a negative at either end of the movement. 

 This necessitates the use of a larger camera, as the images do not 

 come exactly in the same place. 



Explanation of Plates 31 — 33. 



Plate 31. 

 Group of insect eggs, photographed with excentric stop, x 11. 



Plate 32. 

 Diatom, Navicula lyra, x 1,500. 



Plate 33. 

 Polycystina, x 150. 



Journ. Quekett Microscopical dab, Ser. 2, Vol. IX., No. 59, Nov* mbi r 1900. 



