23 THE MICROSCOPIST. 



rangements, as we have said, are more simple. Cheaper 

 instruments, however, are made by English and American 

 opticians, some of which are very fine. 



Opticians divide microscopes into various classes, ac- 

 cording to the perfection of their workmanship or the 

 accessories supplied. The best first-class instruments have 



Fio. 5. f 



Wenham's Prism for the Binocular Microscope. 



a great variety of objectives and eye-glasses, mechanical 

 stage with rack- work ; a sub-stage with rack for carrying 

 various illuminators : a stand of most solid construction ; 

 and every variety of apparatus to suit the want or wish 

 of the observer. They are great luxuries, although not 

 essential to perfect microscopic work. The second class, 

 or students' microscopes, have less expensive stands, but 

 equal optical powers, with first-class instruments. The 



