228 American Petrographwal Microscopes .— Winchelb 
and revolving 
swinging polari¬ 
zer. It is furnish¬ 
ed with two analy¬ 
zers,one to be 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- 
Fig. 5. Acme. 
