ADJUSTABLE OBJECTIVES. 153 



will be no objectives on hand that will not be worth 

 their cost. 



The above programme seems to me to fill the bill 

 as well as any other that could be named, and is prac- 

 tically the same as that followed in my own practice, 

 having daily a large amount of work over urinary de- 

 posits, a considerable portion of which does not require 

 excessively fine definition, and time being very much of 

 an object, I employ, in addition to the glasses named, a 

 oheap, but good and reliable half-inch, say of 35 or 40. 

 With this glass I am enabled to perform much prelimi- 

 nary work over liquids, and am able to dispense with 

 covers, and the objective, from its long working dis- 

 tance, is out of the fumes of the re-agents constantly 

 in use. The half-inch is thus of great service, as a 

 time-saver in short, as a convenience. 



Finally, let it be understood that I have no war to 

 make on objectives of medium apertures. We have 

 stated our experience, and it must pass for what it is 

 worth. The principal point which I desire to impress 

 on the mind of the reader, is that, for the higher class 

 of investigations, the objectives of wide apertures stand 

 alone, unapproachable and unexcelled ; that they alone 

 are the instruments for such work, and this, too, regard- 

 less of the character of the illumination employed, be 

 it central or oblique. Another point is that the use 

 of the high angle enables the observer to cut down the 

 numerical force of the glasses employed, thus saving 

 unnecessary expense. We wish also to render the fact 

 obvious, that a wide angle glass requires time, study, 



