114 



E. M. NELSON ON EVOLUTION OF THE MICROSCOPE. 



The next microscope, Lindsay's (Fig. 22), is a simple microscope 

 with a mirror attached. It has four points of interest : first, its 

 extreme portability ; secondly, its excellent workmanship ; thirdly, 

 it is the first microscope in which we meet with a mechanical 

 arrangement for changing the power ; fourthly, it is the first 

 microscope that was patented. 



Although it has a folding tripod stand to which it can be 

 attached, it is essentially a hand microscope, because the stand 



Fig. 21. 



is too slight and unsteady for serious work. It has stage 

 focussing by means of a lever. 



The powers, which are equi-convex lenses, are seven in number, 

 and are burnished into two slips of metal, four being in one 

 and three in the other; these slips fit in a groove behind an 

 eye-hole, the power being changed by merely shding the slip to 

 a mark engraved on it, which denotes the power. A sliding 

 slip of powers became afterwards a rotating wheel of powers, the 

 prototype of the revolving nose-piece of the present day. It 

 should be noted that these slips have a small spring fastened 



