MICROSCOPY. 443 
men from moisture by drying or preferably by passing successively 
through weak and absolute alcohol, treats it with oil of cloves 
which is more desirable than turpentine because more readily mis- 
cible with balsam and not calculated to harden the specimens even 
if they are left in it for a long time, transfers it to the slide and 
arranges it with needles, places a drop of the balsam solution on it 
and applies the glass cover in the usual manner. In a few days 
the mount will be sufficiently hardened to be handled with safety, 
especially if after twenty-four hours it should be slightly warmed 
and the cover carefully pressed down with the forceps and held 
down with a small weight. The best finish for the edge of the 
circle he finds to be the same balsam that is used in mounting, laid 
on with a camel’s hair pencil ; since this is neat and handsome, and 
will not spoil the specimen by running in, as may happen with col- 
ored varnishes. 
Uxmountep Microscoric Ossecrs.—Mr. Jno. H. Martin, of 
Week street, Maidstone, England, is supplying a great want of 
microscopists by furnishing unmounted objects for the use of 
amateurs. His price for two dozen objects, post free, to the 
United States, is one dollar. 
Reso.urion or Frustutia Saxonica INTO Rows or Dors. After 
my new Tolles 4, immersion had resolved the lines of Amphi- 
pleura pellucida into beading, I succeeded in obtaining a slide of 
Frustulia Saxonica, mounted dry by J. D. Moller. This test is 
Somewhat easier than the Amphipleura, but more difficult dry than 
Grammatophora subtilissima is in balsam, or at least I find it so 
by lamp light, although both are satisfactorily shown. The fol- 
lowing measurements were made with the Tolles jj; objective, 
No. 2 eye-piece, and camera lucida ; amplification 4000 times. 
Using an ammonio-sulphate of copper cell and sunlight, the 
transverse striæ of the Frustulia are brought out without the least 
difficulty. The average number of lines to the thousandth of an 
inch, in fifteen measurements on different frustules, was eighty- 
nine. This agrees essentially with the counts of Dippel and Dr. 
Woodward. 
I also succeeded in bringing plainly to view longitudinal lines 
Which were counted in the same way. The average of fifteen 
counts was ninety-five to the thousandth of an inch. The lowest 
number observed was eighty-eight, the highest one hundred. 
