SPECIAL MICROSCOPES 



263 



made instrument of the same size with a liar movement. But if we 

 compare the range of prices as presented by English and American 

 makers, we rarely find an equivalent difference in cost. 



Then the tyro will lie warned by this not to purchase a pretentious 

 instrument with a bar movement and mechanical stage for, say, 51. 



But if a low-priced 

 instrument is to be 

 jmrchased, if, as is 

 almost certain, it be a 

 Jackson model, see 

 that it has a rack- 

 work coarse adjust- 

 ment, eschew the short- 



lever 



nose-piece, 



and 



have a differential 

 screw fine adjustment, 

 a large plain sta^r. 

 and an elementary 



centring 



sub-stage. 



Such an instrument 

 should be obtained for 

 51. 10s. 



Although not fre- 

 quently used, it would 

 lie doing our work im- 

 perfectly not to refer 

 to a form of micro 

 scope devised for 

 chemical purposes by 

 Messrs. Bausch and 

 Lonib. The object of 

 Prof. E. Chamot, of 

 the Cornell University, 

 in inducing these op- 

 ticians to make this 

 microscope was, 

 says, to enable 

 chemist who 

 mastered the use of the 

 microscope ' to employ 

 the elegant and time- 

 methods of 



he 

 the 

 had 



FIG. 206. Microscope for chemical purposes (1897). 



saving 



micro-analysis,' thus 



giving him ability ' to 



examine qualitatively 



the most minute amounts of material with a rapidity and accuracy 



which are truly marvellous, not to speak of the many substances 



for which 110 other method of identification is known.' 



An illustration of this instrument is given in fig. 206. It will 

 be observed that it follows the Continental model ; since in all the 

 work for which it is intended the stand is always used in an upright 



