American Petrographical Microscopes. — Winchell. 225 
the Shenandoah valley which Prof. Rogers supposed to be 
Potsdam. 
AMERICAN PETROGRAPHICAL MICROSCOPES. 
By N. H. Winchell. 
Three American firms now advertise petrographical micro- 
scopes made in this country.^ That which gave microscopical 
petrography its first important impulse in America was the 
publication in 1876 by the U. S. government of the work of 
Zirkel on the eruptive rocks collected under Mr. Clarence 
King by the survey of the fortieth parallel. This was written 
and engraved if not printed in Europe. On the distribution 
of this beautiful quarto volume (Vol. VI of Mr. King's report), 
a comparatively new geological domain Avas revealed to the 
American student. He was not backward in entering upon its 
exploration. Soon afterward the pioneer of American publi" 
cations in microscopic petrography appeared as a chapter in 
one of the final volumes of the New Hampshire geological sur- 
vey prepared by Dr. Geo. W. Hawes under the direction of 
Prof. C. H. Hitchcock. There began with this to be a demand 
for American-made petrographical microscopes. Several foreign 
instruments were in use in the laboratories of American stu- 
dents. The cheaper grades were found to be defective and the 
higher class instruments were too expensive. Several styles 
were announced in England before any attempt was made in 
America. The first English work designed for student's use 
was that of Mr. Frank Rutley ( The Study of ^oc^"*, published 
in London in 1879) and it called attention by special descrip- 
tion to an English-made microscope, manufactured by Watson, 
Pall Mall, London. 
When the examination of the crystalline rocks was begun by 
the Minnesota geological survey in 1878, it was essential that 
this method of research should be resorted to. The first in- 
strument owned by the survey was a Tolles Studenfs Stand, 
remodeled for petrography in New York under the special di- 
rection of Prof. A. A. Julien of the Columbia College School 
of Mines. As this lacked some of the appliances needed, re- 
sort was had to American makers, but none would undertake 
to construct a microscope adapted for petrographical research 
' W. H. Bulloch, 99 W. Monroe St., Chicago, 111. ; Jas W . Queen & Co., 9J4 Chestnu 
St., Philadelphia, Pa.; and the Bausch-Lomb Optical Company, Uoehester, N. Y. 
