68 



THE MICROSCOPE 



quantity is not always available, and recourse must be 

 had to oil lamps, gas lamps preferably those with 

 incandescent mantles and electricity; and of these 

 the last is undoubtedly the best. A handy lamp 

 holder which can be manufactured in the laboratory 

 is shown in Fig. 60. It consists of a base board 

 weighted with lead to which is attached the ordinary 

 domestic lamp holder, and behind this is fastened a 



FIG. 60. Electric microscope lamp. 



curved sheet-iron reflector. An obscured metal fila- 

 ment lamp of about 16 candle power gives the most 

 suitable light, and if monochromatic light is needed, 

 the blue grease pencil is streaked over the side of the 

 lamp nearest the microscope; the current is switched 

 on and when the glass bulb is warm, rubbing with a wad 

 of cotton-wool will readily distribute the blue greasy 

 material in an even film over the ground glass. 



