50 HOW TO SEE WITH THE MICROSCOPE. 



ject slides ; revolving diaphragm ; concave mirror, with 

 movement to give oblique light, and for the illumina- 

 tion of opaque objects the mirror is removed to an up- 

 right stand. The coarse adjustment for focus is effected 

 by sliding the compound body which is held in its place 

 by a spring; fine adjustment by a movable plate and 

 screw on the stage, which is efficient with high powers. 

 . The stand is made with all the care bestowed on his 

 first-class instruments. The form is that of the Jackson 

 pattern. To this instrument Mr. Tolles supplies several 

 variations and additions, as a matter of course increas- 

 ing the cost as well as its capacity. Among these sev- 

 eral extras may be mentioned sliding stage, giving ver- 

 tical and horizontal motions by hand, and adapted to 

 the use of the " Maltwood Finder;" sub-stage for acces- 

 sory apparatus; fine adjustment by lever and microm- 

 eter screw; rack and pinion for coarse adjustment ; thin 

 glass stage to rotate on the optical axis ; the stand en- 

 tirely of brass, etc. For a " student's stand " this is an 

 instrument of good round proportions. It stands firmly 

 on its legs, and the stage is remarkably roomy. The 

 body-tube is nickel-plated, and the entire instrument 

 symmetrical in its proportions, and not without pre- 

 tensions to style. Like all of Mr. Tolles' work, it is 

 made " for keeps." There are many of them in use and 

 doubtless giving satisfaction. 



The Bausch & Lomb Optical Company manufacture 

 several excellent stands, which were designed under the 

 immediate superintendence of Mr. Earnest Gundlach. 

 The firm furnish some seven or eight models, Irom 

 which we select the folio wins: three : 



