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SUMMARY OF CQRRENT RESEARCHES RELATING TO 



fitted to its side. For this method, the lamp and bull's-eye are adjusted 

 as in Method I., care being taken that proper distances are kept, when 

 the same effect will be produced as with a stop or diaphragm placed 

 immediately over the vertical illuminator. 



C. Baker's Electric Lamp for the Microscope. — This illuminant 

 consists of a Nernst electric lamp (fig. 50), mounted upon a heavy 

 tripod stand, the feet of which are corked. It is capable of adjust- 

 ment in a vertical direction, and there is also a tilting movement, to 

 enable the lamp to be used at any angle required. 



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Fig. 50. 



There are three parts to the Nernst lamp, namely, the lamp holder, 

 containing an automatic cut-out ; compensating resistance (a small glass 

 bulb containing a fine spiral wire) ; and the filament itself, mounted on 

 porcelain, and having an electric heater behind it. 



These lamps are made for use on two currents, namely, 100 volts 

 and 200 volts, and are provided with either plug or bayonet-joint 

 connections. 



The globe covering the luminous filament is blackened, leaving 

 only a small aperture in front, through which the light passes. 



Coloured and ground-glass screens, for modifying the light, are 

 carried in front of the globe by means of a removable carrier. 



