186 



THE MICROSCOPE. 



among us who have gas at command will, no doubt, give 

 it the preference on account of its convenience, and 

 freedom from all kind of trouble. An excellent form of 

 gas-lamp is Highley's (fig. 109). 



The mono-chromatic gas-lamp, fig. 110, is very useful and 

 most economical. Gas, as a source of light, presents great 

 advantages over oil and spirit, on account of cleanliness, 

 being ever ready for use, and affording a perfect control 

 over the flame ; but when the ordinary gas-iamps are used 



Fig. 110. Gas-lamp arranged for itse. 



for the purpose of illuminating the field of the micro 

 scope, a yellow glaring light is given, alike injurious to 

 the eye and the definition of the object under examina- 

 tion. To correct these evils, this lamp was arranged, which 



