196 HOW TO SEE WITH THE MICROSCOPE. 



was thus shoved to the left the definition was improved, 

 but we were compelled to desist from this movement 

 owing to the loss of light, and were therefore content 

 with the lamp as far to the left as was possible without 

 sacrifice of the illumination. Of course the objective 

 was adjusted with all possible care, the collar standing 

 within three divisions from " open point." 



We now carefully raise the objective, and removing 

 the water with a bit of blotting paper, we substitute a 

 drop of glycerine, focussing and adjusting the glass 

 again with the glycerine intermedium ; the glass now ad- 

 justs at nearly closed, the collar having made nearly two 

 full revolutions from its former position. It is further 

 obvious that we have now more light generally; we 

 can, too, move the lamp to a greater distance right or 

 left without loss of illumination. In fact, things in 

 the tube have a sunshine appearance that is very accept- 

 able. We now attempt again the resolution of the 

 same shell, using the blue field as before. Finding that 

 the lamp will bear to be shoved further to the left than 

 before. And now, even before arriving at the limit of 

 light, i. e., the lamp not so far to the left as we might 

 place it, we are rewarded by a splendid display of the 

 transverse striae, this, too, with illumination, I was 

 going to say in excess, at all events enough to allow the 

 use of the one-halt and the one-fourth solid eye-pieces. 



We have thus described this experience taken from 

 our private practice, giving the actual results obtained. 

 Well, now, suppose that with the Wenham reflex the 

 experiment had turned out a total failure; i. e., that we 



