184 THE AMERICAN MONTHLY [June, 



from the cheaper and softer gelatins in common use, manufact- 

 ured from the trimmings of slaugliter house pelts. 



It is filtered. It is perfectly transparent, and will not change 

 color in the slide. Unlike glycerine it stays where you put it. 



DIRECTIONS. 



1. Work in a warm room, the jelly is hard and cools rapidly. 



2. Heat, and keep hot while using, in a warm bath. 



3. Mount from chemically pure glycerine and 75 per cent 

 alcohol, one volume of each, kept till perfectly homogeneous, 

 and filtered. 



4. Warm the slide and place the jelly on it with a glass rod, 

 kept clean. 



5. Place the object in the jelly, being sure that it is well cov- 

 ered. This may require an additional drop. 



6. Hold the object in place and drain the slide to get rid of 

 the glycerine and alcohol. 



7. Cover the object again with jelly and examine carefully 

 under the dissecting microscope for air bubbles, especially for 

 stowaways. Air bubbles should be Avorked off" with a dissecting 

 needle and not picked out with the forceps. 



8. Cover the object again — take the cover glass between the 

 thumb and finger, — breath on it. — cover it well with jelly, — 

 take it by the edge with the forceps, — turn it over quickly, — 

 place it gently on the object at an angle and apply a clip. 



If it is desirable to mount more than one object in a slide, 

 place them in just jelly enough to cover them safely from air, 

 and give time to harden, after which an additional layer may 

 be added and the cover placed as before and held with a clip 

 Next pass the slide over a spirit lamp till the entire mass of 

 jelly is melted. If the right quantity has been used the objects 

 will not slide out, or if they become displaced push them back 

 again with a slip of pointed paper slightly moistened in the 

 mouth. No number of directions will supercede patience, prac- 

 tice and good judgment. 



A Modified Microscope. — Mr. Hodgson, of Birmingham, 

 England, has had Swift & Son construct an instrument with 

 the following modifications : 



1. The drawtube and milled heads are of aluminum. 



