228 American Petrographical Microscopes. — Winchelh 
and revolving 
swinging polari- 
zer. It is furnish- 
ed with twoanaly- 
zer8;one to he used 
at the upper end 
of the tube with 
a graduated rim 
and indicator, and 
the other placed in 
a sliding brass box 
which enters the 
body of the tube 
just above the ob- 
jective. A Klein 
quartz plate is 
mounted in a sim- 
ilar way and slides 
in another slot just 
below in the nose- 
piece. The eye- 
piece is furnished 
with crossed spi- 
der-lines, and re- 
ceives at the upper 
end a circular calc- 
spar plate for stau- 
roscopic examina- 
tion. This instru- 
ment is illustrated 
by the figure 5. Its 
cost with two ob 
jectives is $125. 
The Bausch- 
LombOpticalCom- 
pany,Rochester, N 
Y., introduced the 
third lithological 
model in Decem- 
ber, 1887. This was 
designed and con 
Fir 5 Ac Ml- 
