SPECIAL MICROSCOPES 



26 3 



made instrument of the same size with a bar 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 be warned by this not to purchase a pretentious 

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



But if a loiv-priced 

 instrument is to be 

 purchased, 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 stage, 

 and an elementary 

 centring sub-stage. 

 Such an instrument 

 should be obtained for 

 51. 10s. 



Although not fre- 

 quently used, it would 

 be doing our work im- 

 perfectly not to refer 

 to a form of micro- 

 scope devised for 

 chemical purposes by 

 Messrs. Bausch and 

 Lomb. The object of 

 Prof. E. Chamot, of 

 the Cornell University, 

 in inducing these op- 

 ticians to make this 

 microscope was, he 

 says, to enable the 

 chemist who had 

 mastered the use of the 

 microscope ' to employ 

 the elegant and time- 

 saving methods of 

 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 no 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 







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



