= 4 ben ti e's Saas ae 
144 THE MICROSCOPE. . 
tin pill-box lid of a size to just cover the bottle. Pass the 
twisted wire through this, and have a tinner make it fast with 
solder. 
This medium needs a little warming, about 110° Fah., to make 
it fluid for use, which is easily done over a common kerosene lamp. 
A little ingenuity will construct some kind of scaffold to hold a piece 
of heavy sheet iron about an inch above the lamp chimney ; on this 
place a flat tin box, or pan 4x 8, x 4 inch deep, filled with sand. A 
tin cover lid over this makes a cheap and very satisfactory warming 
plate, on which the working bottle can be placed, and in a few 
minutes is ready for use. Even an empty tin fruit can with 
a little sand in the bottom, may form a substitute. However, some 
kind of warm plate is indispensible to him who would prepare 
microscopic slides. 
I have a few dozen slides made in this medium ‘several months 
ago, “neglected,” of a ring of cement, to test it in comparison with 
Farrant’s medium, and I find it just as good in this particular; as 
the latter does not take in air by drying under the edge of the cover, 
as does the glycerin jelly mount, when thus neglected, when 
enough of the solution is placed on the section. Both this and the 
Farrant’s will take in air by retraction when too little of the solution 
is used. 
It is a much better working solution than Farrant’s. When we 
wish to mount several specimens under one cover without fixing, it 
flows as nicely as soft balsam or glycerin; while the Farrant’s solu- 
tion, being a viscid medium, displaces the sections, even floating them 
out from under the cover, and it is more prone to leave large air 
bubbles. 
Furthermore, theoretically, my solution ought to be a better 
preserving medium, glycerin being the preservative. 
My Solution—Glycerin, 56 per cent.; water, 25 per cent.; 
gelatin, 5 per cent.; gum arabic, 14 per cent. 
Farrant’s Medium—Glycerin, 20 per cent.; water, 40 per cent.; 
gum arabic, 40 per cent. 
The above formula of glycerin jelly gives glycerin 50 per cent. ; 
water, 35 per cent.; gelatin, 15 per cent. Kaiser’s glycerin, a 
much used form, gives glycerin 50 per cent.; water, 43 per cent. ; 
gelatin, 7 per cent. 
The heat required to liquefy my medium is not great enough to 
injure the most delicate tissues. Place the mounted slide in a dry. 
ing box; it sets in a few days so as to hold the cover glass firmly, 
after which, at any convenient time, fasten it with a ring of shellac 
