THE MICROSCOPE. 127 
carefully made cells. Fluid mounts which show signs of failure 
should, as a rule, be immediately remounted. The presence of air 
seems to facilitate decomposition. Frequently the bubble is a 
gaseous result of internal decomposition, which progresses in spite 
of liberal coats of varnish subsequently applied. Glass slips, with 
concave centers, should be preferred for many objects. They cost 
about the same as loose glass cells, and are deep enough for a head 
of Tenia Solium, etc., and the addition of a ring of thick shellac, 
well dried, would form a cell deep enough for a wide range of 
objects. All fluid mounts ought to be revarnished every year, 
whether they show signs of failure ornot. King’s Amber or Brown’s 
Rubber, are transparent varnishes, and neither will impair the 
beauty of any fancy finish. White and black finishing varnishes 
may be made by adding to shellac varnish, tube oil color, ivory black 
or zine white. The resulting finish does not crack, but is not as 
brilliant as zinc cement or asphaltum. The surface of a glass slip, 
to which a cell is to be cemented, should be well cleaned with a mix- 
ture of equal parts alcohol and chloroform. The best cement would 
fail to adhere on a dirty glass surface. | 
Very Truly, 
S. G. SHANK. 
Apany, N. Y. 
P. S.—Your March number makes a first-class ‘‘ specimen 
copy.” Send it around to the outsiders. It is a rich number. 
Answer 14.—Your correspondent states that the so-called fraud 
of the Calvert Company, Md., relating to fertilizers, was exposed by 
the U. 8. Department of Agriculture. I think this is erroneous. Mr. 
Phinn, of New York, the well-known microscopist, was the first, I be- 
lieve, to expose the erroneous views of the Calvert Company in re- 
gard to the value of the admixture of diatomacaeous earth with fer- 
tilizing substances. He called my attention to thesubject about ten 
years ago, but I did not write about it, considering that the article 
published by the company carried with it its own condemnation. 
Yours Very Truly, 
THomas Taytor, M. D. 
4, (Ans.)—Mr. Walter White, Litcham, Swaffham, Eng., pub- 
lishes a list of over 172 botanical preparations which he has for sale. 
I have tried these and know them to be good, and can recommend 
them to your correspondent who asks for such. 
W. H. Seaman. 
