THE MICKOSCOPE 



29 



phragm, also a triple nosepiece. The last, although not 

 absolutely necessary, is a great time-saving arrangement, 

 which not only saves the necessity of unscrewing the 

 objectives to obtain variations in power, but also pre- 

 serves the objectives from much wear and tear. For 



Fig. 1. — The Microscope. 



ordinary work the following objectives are required : 1 inch, 

 ^ inch, and a yV inch oil immersion. These objectives 

 combined with an ' A ' and ' B ' eyepiece will give magnifica- 

 tions of from 50 to 1,100 diameters, which is ample for all 

 ordinary purposes. 



It is essential to be provided with a brilliant source of 

 illumination for the examination of bacteria, particularly 



