THE MICROSCOPE. 185 
following day the balsam will have become thick from evaporation 
of the benzol. Now place a drop of fresh balsam on the slide, invert 
cover-glass over it, and the mount is ready for ringing as soon as 
the balsam is dry. Dry mounts should be made in cells, the scales 
having previously undergone the same treatment. 
PREPARING SECTIONS OF SEIN AND Scazp. (Cote )—Place the skin 
in equal parts of alcohol and water for thirty-six hours ; then in 
alcohol until required. After sectioning, stain first in following, for 
5-10 minutes: 
Pure carmine, 50 grains. 
Strong ammonia, 120 minims. 
Dissolve carmine in ammcnia in a test tube, by aid of gentle heat if 
necessary ; filter and add filtrate to four ounces saturated solution 
borax. After staining, wash sections in alcohol and then transfer to 
acidulated alcohol (5 parts to 1 HCl). Wash out acid for one 
hour in alcohol, and then stain in sulph-indigotate of soda for four 
or more hours. To make this, use a saturated aqueous solution of 
the sulph-indigotate of soda, and add two drops to the ounce of alco- 
hol when required for use. Clear sections in clove oil and mount in 
balsam. 
Crystats as Micro-Ogsecrs.*—Crystals of the various metals 
furnish interesting and often beautiful objects for the microscope, 
and as they are, for the most part, easy to prepare, quite a variety 
may be kept on hand for “show” purposes, if not for their scien- 
tific value. Prof. John Bolton, of Cleveland, furnishes two such 
slides to Box L, Am. Postal Micro. Club. He says: Silver may be 
precipitated from the nitrate by arsenic, antimony, bismuth, zinc, 
tin, ete. Copper from the chloride by bismuth, zine, tin, lead and 
iron. Gold from the chloride with the reagents mentioned under 
silver. (By consulting a good work on chemistry, many methods of 
obtaining crystals may be found.—Enrrors. ) 
Improved Porariscope.t—At a recent meeting of the London 
Physical Society, Dr. S. P. Thompson advocated a polariscope formed 
from a rectangular block of spar, two faces of which are perpendic- 
ular to the optic axis, two cuts parallel to the axis are made from 
the middle of one side to the ends of the opposite, and the surfaces 
polished and cemented with Canada balsam. A short prism with 
wide angle is thus obtained, which can be readily fitted to the 
*Am. Postal Microscopical Club’s Note book, 1888. 
+Scientific American, Feb. 1, 1888, p. 69. 
