jon MICROSCOPE. . 95 
CORRESPONDENCE AND QUERIES. 
CORRESPONDENTS IN ANSWERING QUERIES WILL PLEASE REFER TO 
NUMBERS ONLY. 
Bristot, Conn., Jan’y Ist, 1889. 
Editors Microscope : 
I have been much interested in the article in your January 
number on cleaning diatoms by F. W. Weir. 
He says that the process given “is more satisfactory than any 
published method with which he is familiar.” I would call his 
attention to an article published in the April, 1887, number of the 
American Microscopical Journal, in which the so-called “ cold pro- 
cess ” 
is given in minute detail. 
I had invented and used the process with great satisfaction for 
some time, and finding, by correspondence with many of the princi 
pal professionals and experts, that such process was needed, I pub- 
lished it as orginal in the above mentioned journal. 
The shaking and sanding process had been previously published 
in the same journal by Dr. Geo. H. Taylor of Mobile, Ala., but he 
subsequently announced that he had found the shaking destructive. 
I would remark that if material containing the larger Pleurosig- 
ma, for instance, were subjected to the shaking described by Mr. Weir, 
not one in a hundred. of these forms would remain unbroken, and 
the method described would be nearly as destructive to many of the 
larger or longer fresh-water varieties. 
Yours truly, Wm. A. Terry. 
14. ‘If I remember rightly, the poplein deposit of Calvert Co. 
Md., was first brought to notice by an attempted fraud to place it 
upon the market as a fertilizer, the markings of the guard cells of 
the silicious cuticles of the gramineze being adduced to show that 
the silicious forms found in this earth are necessary to plant nutri- 
tion. The fraud was exposed by the Agricultural Department. Will 
some one kindly refer me to the volume of the Agricultural Reports 
where this account is given? 
M. B. 
15. Tue Use or Diappracms.—I would like to hear an expression 
from your readers in regard to the use of diaphragms. Some micro- 
scopists claim that they are useless, while others will not work with- 
out this accessory. I understand that no diaphragm is supplied 
with the Griffith Club Microscope, unless especially ordered. 
H. M. W. 
