THE BACTERIOLOGICAL MICROSCOPE. 77 



the flat of the flame may be utilised. Great care should be taken 

 to have the wick evenly trimmed. The best paraffin oil should 

 be burnt, and it is as well to add a small lump of camphor. The 

 metal chimney has an aperture in front, giving exit to the rays of 

 light, which is closed in by a slip of glass. The glass is very liable 

 to crack when exposed to the full force of the flame, and it is as well, 

 therefore, to be provided with a stock of glass slips, which have 



FIG. 22. LARGE MICROSCOPE LAMP. 



been annealed by being enveloped in a cloth and boiled for two or 

 three hours. 



The flat of the flame is used with low powers. The image of 

 the flame is reflected by a plane mirror, and a bull's-eye condenser 

 interposed between the lamp and the mirror to give an equal 

 illumination of the whole field. In working with high powers the 

 lamp is turned with the flame edgewise, and the mirror is dispensed 

 with. By working, as it is termed, directly on the edge of the 

 flame, the illumination is greatly increased, and a band of light can 



