138 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



still greater when there is only a very limited number or even only 

 one specimen of an object. 



Dr. Viguicr's new form is intended to remove this inconvenience. 

 It has no fixed glass plates, the ordinary slide and cover-glass being 

 used. When the observation is over, the preparation is withdrawn 

 just as it has been seen, and drawn or photographed or subjected to 

 reagents, and definitively preserved. The management of the instru- 

 ment is, moreover, very simple. 



The compressor is shown in figs. 24 and 25, and it will be seen 

 that for the motion of the upper plate the slow-movement screw is 



Fig. 25. 



used which is found in so many Continental Microscopes and in 

 Moulinie's compressor, the directing pivot / of the latter being, how- 

 ever, much longer, and placed on the side furthest from the glasses. 

 The important point claimed by the author is the adjustment and 

 removal of the glasses. 



The bar which turns on a is opened, and the slide g is introduced 

 (resting in a deep groove of the lower plate), its ujjper surface being 

 entirely free except at the ends, where are four springs r and r' to 

 keep it in its place. Two of these are attached to the movable bar a, 

 which is closed after the introduction of the slide. 



To fix the cover-glass, take the copper wire which has a little ball 



Fig. 26. 



as a reservoir of heat (fig. 26), and slightly warm it over the spirit- 

 lamp, and place a very little drop of paraffin under the four arms e of the 



