2 1 8 PR A CTICAL MICROS COP Y. 



to set up the battery and work the electric lamp, unless 

 it was desirable to work at night or in unfavourable 

 weather. 



For the production of the electric light, Duboscq's lamp 

 was used, set in motion by a battery of fifty small Grove's 

 elements, and with this source of light photographs can be 

 taken with any power with which pictures are possible 

 in sunlight. The rubber cups of the battery were 4! inches 

 high, 3J inches wide, and 2 inches thick ; the platinums 5^ by 

 2i inches, and weighed about 60 grains each. The zincs 

 were bent on themselves so as to present a part of their 

 surface on each side of the platinums, and weighed when 

 new about a pound each. 



FIG. 



The electric light as hitherto employed has been a 

 cumbrous, expensive, and troublesome process, which 

 certainly could not be employed by the majority of per- 

 sons wishful to practise photo-micrography. For those 

 who may have to use high powers, and to whom daylight 

 is not accessible, the magnesium light seems to possess 



