CHAPTER II. 



THE MICROSCOPE STAND. 



As we are supposed to be treating nearly exclusively of 

 compound microscopes that is to say, of instruments in 

 which the amplification of an object is produced by means 

 of a combination of lenses called an " objective," the image 

 being further magnified by another set called an " ocular " 

 or " eye-piece " we will consider that our readers require 

 no demonstration as to the necessity of some mechanical 

 contrivance for holding these lenses in their correct 

 positions. 



This is the office of the stand of a compound microscope, 

 and when we notice the progress which has been made in 

 the details of this instrument from the time the first was 

 made for sale in England by Mr. John Marshall, we shall 

 find that not to opticians only, properly so called, are we 

 indebted for improvements, but to mechanicians equally. 

 It was but of little use attempting to perfect the optical 

 arrangements while the mechanical contrivances were 

 imperfect, and when this was fully appreciated, real 

 improvements were made by mechanics and optics working 

 hand in hand. At the same time, we must not forget the 

 aid which has been rendered by amateurs and micro- 

 scopists with unlimited means at their disposal; it is 

 certain that many of the early and even the more recent 

 improvements would not have been executed, except at 

 the instance of one possessing a well-lined purse and with 

 great interest in the science. 



