76 



BACTERIOLOGY. 



for general use, it is the best form of artificial illumination for the 

 microscope. 



An ordinary parafiin lamp of the cheapest form may be used, 

 but there are many objections to it, such as the shape of the 

 chimney, and the strise and defects in the glass. The best form of 

 paraffin lamp is constructed by Baker and by Swift from sug- 



FiG. 21. — MICBOSCOPE Lamp. 



gestions by Nelson and Dallinger (Fig. 21) ; there is also a similar 

 but much larger pattern which is made by Swift (Fig. 22). This 

 form of lamp has a large flat bowl for the oil. It is attached to 

 a standard, and can be raised or lowered to the desired position. 

 The chimney is of metal and blackened, so that there is no reflected 

 light, and it may also with advantage be provided with a shade, 

 so that no light reaches the eye except through the microscope. 



The burner may be made to revolve, so that either the edge or 



