210 THE MICROSCOPE. 
soluble in water and glycerin, except No. 7. The objections to Far- 
rant’s medium are: it soon colors from age, is not as clear and trans- 
parent as the resinous cements; it dries too slow. 
I do not wish to recommend my media to microscopists until I 
have given them a satisfactory trial, and all slides that I have sent 
out can be returned if the media is unsatisfactory. Thus far none 
have been returned. 
THE FINAL CLEANING OF SLIDES. 
After the slides have been temporarily cleaned with spirits of 
turpentine and benzine and hardened, place them on a turn-table 
and moisten the slide with water on a brush, and hold a sharp 
brass, or iron scraper, on the slide while it is revolving rapidly, 
which loosens the thin film of the medium which the benzine could 
not remove around the mount. Scrape or loosen the rest without. 
revolving the slide, which can then be cleaned and polished, or 
rubbed dry with strips of thick, solid harness-leather, one-half inch 
wide and three or four inches long, one end cut square at right 
angles and the two corners of the other end cut off to a point like 
the end of a knife-blade. When the ends get soiled wash them or 
shave them to get a fresh and clean surface of leather. The pointed 
end will then be in a good shape to clean and rub dry the covers 
moistened with water if soiled by using four or five of them. The 
leather can be kept clean and dried by rubbing their ends rapidly 
on a wollen cloth stretched over a board three or four inches square. 
One or two blocks covered with linen rags are also useful in cleaning 
and rubbing mounted slides to a dry polish after the scraper has 
been used with cold water. This scraper should be made of sheet 
brass, or heavy hoop-iron three-eights of an inch wide and four or 
five inches long, the ends and edges beveled sharp as a chisel. Steel 
might scratch the slides or covers, even if not hardened. 
The scrapers should be kept sharp at all times with a sharp file. 
A polished slide can be held between thumb and finger without 
finger prints, by holding it between a clean piece of folded paper. 
DOUBLE-STAINING ANIMAL TISSUES. 
Kidney, lung, ete., may be double-stained beautifully as follows: 
First, stain them in a solution of ‘Bengal blue,” dissolved in 
distilled water, so that it will have a medium blue color when 
written on white writing paper with a clean pen. Give it several 
hours’ time to dissolve, and filter. 
Then make a red stain, as follows: 
Put scme ponceau (diamond dyes) into a clean, dry test-tube. 
