722 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The author says :— ;.-■., t.x 



" To use the finger, the point of the glass thread is first brought 



into the focus of the objective, or nearly so, by sliding the tube on the 



vertical rod, and pushing or pulling the rod carrying the thread 



until the desired position is attained. It is not difficult to do this, 



Fig. 140. 



and having once been done by hand, it does not have to be repeated, 

 as all further movements are made by the adjustments of the Micro- 

 scope. Supposing now the point of the glass thread to be in focus ; 

 by means of the fine adjustment throw the focus ahead of the point, 

 then, by means of the coarse adjustment, rack down and search for the 

 object you wish to pick up. Having found the object desired, again 

 bring the point of the thread into focus by means of the fine adjust- 

 ment ; then rack down with the coarse adjustment and pick it up. 

 Now rack back with the coarse adjustment, remove the slip on which 

 the material is spread, and place your prepared slip or cover upon the 

 stage. Again, by means of the fine adjustment, throw the focus 

 ahead of the object, rack down with the coarse adjustment, and search 

 for the spot where you wish to deposit the object, and having found 

 it, again focus the object, then rack down with the coarse adjustment, 

 and when the object touches the slide and has been placed in proper 

 position, fix it by means of a very gentle breath. I prefer this mode 

 of fixing instead of the arrangement of tubes proposed by Professor 

 Smith. 



I coat the surface of the cover or slide upon which the diatoms 

 are to be fixed with an exceedingly thin film of gelatine, prepared 

 thus : — Dissolve 2 drachms of Cox's gelatine in 10 drachms of acetic 

 acid by the aid of a gentle heat. When the gelatine is thoroughly 

 dissolved, add 1 drachm of alcohol and 1 oz. of distilled watery stir 

 well until thoroughly mixed, let stand some hours, and filter through 

 the finest filtering paper. Keep in a glass-stoppered bottle. To coat 



