WORKING WITH LOW POWERS. 229 



For ordinary work by daylight we use the plain mir- 

 ror in conjunction with the condenser; and let me here 

 again insist that the latter be such as has already been 

 described, i. e., of low aperture, admitting but a narrow 

 cone of light. In very dark days the light can be rein- 

 forced by employing the concave mirror, a plan not gen- 

 erally recommended, but nevertheless quite practicable. 



For reasons before given, we greatly prefer, for regu- 

 lar right straight along daily work, to use the stand 

 with the tube short, keeping, for the most part, the 

 tube vertical, dispensing, too, with the stage clips, and 

 simply laying the preliminary mount thereon, shoving 

 it about in every direction required, by the fingers. 

 Those who have been accustomed to confine the slide 

 under the clips, as is generally done, will not, on the 

 first trial, be likely to endorse my practice. Let me, 

 then, to all such, especially recommend it. By thus 

 allowing the slide to rest by its own gravity alone, one 

 soon acquires a delicacy of finger manipulation that is 

 of very general value; while, per contra, the clips are a 

 real hindrance to fast work. Those who have the pa- 

 tience to practice without them for one solitary week 

 will not be likely to get back into the old rut. 



The height of the work table should vary with that 

 of the observer ; such a table as one would naturally 

 elect to write on will be about the correct height for 

 microscope work. This, if the low angled condenser is 

 to be generally employed, may be placed at a consid- 

 erable distance from the window, but care should be 

 taken that the light conies from the left. If there be 



