THE BACTERIOLOGICAL MICROSCOPE. 



75 



bacteriological microscope, with a cheap form of adjustment to the 

 sub-stage condenser, at a total cost of about fifteen pounds. 



Method of Illumination. Good daylight is the best for 

 general work. The microscope should be placed near a window 

 with a northern aspect. Direct sunlight should never be utilised, and 

 the best light is that reflected from a white cloud. When daylight 

 is not available good results can be obtained with either gas or a 



FIG. 20. ABBE'S CONDENSER CONSTRUCTED BY ZEISS. 



paraffin lamp. In the author's laboratory the microscope lamps 

 are fitted with Welsbach incandescent mantles. These have many 

 advantages over an Argand burner or a paraffin lamp. A steady 

 and beautifully white light is obtained, and the lamps are quickly 

 lit, and require comparatively little attention. In using high powers 

 and carefully focussing the sub-stage condenser, the image of the 

 fabric of the mantle is embarrassing, and is an objection to this 

 light for the most accurate observations, but in other respects, and 



