98 



scientious optician has his standard for every objec- 

 tive which is his guide. 



In purchasing a microscope a beginner may be eas- 

 ily misled by the enticing appearance of an object, 

 which may be due not so much to the instrument as 

 to the object itself, and if the optical parts are infer- 

 ior, it will require but a short experience to become 

 convinced of it usually as soon as a comparison can 

 be made with reliable work. The investment in one 

 of these objectives is not only a source of disappoint- 

 ment, but usually proves to be a pecuniary loss, as it 

 is usually followed by a fresh outlay in responsible 

 work. 



It is of ordinary occurrence that such objectives as 

 have just been spoken of are sent to the writer's firm 

 with the request to examine them and rectify the 

 faults ; but an examination almost invariably proves 

 that the cost of doing this is considerably greater 

 than purchasing a new objective of the same power, 

 and it would not even then be equal to the latter. 



Accessories. As has been stated before, one of 

 the most useful accessories to the stand is the glass- 

 stage and slide-carrier. 



Another accessory which is in equal demand, and 

 deservedly so, is the double nose-piece. By means of 

 it two objectives may be kept permanently attached 

 to the microscope, avoiding any loss of time from 

 changes. When properly fitted, an immediate change 

 can be made with the additional advantage of having 



