cai a 
12 Tur Microscope. 
BULLOCH’S LITHOLOGICAL MICROSCOPE STAND. 
le general construction, as shown in the illustration, is simi- 
lar to the professional stand except in the following details: 
There are two stages, one with plain sliding object carrier. 
Each stage is graduated to fifteen minutes, and reading by a 
vernier to twenty seconds, and can either be resolved by hand, 
or by tangent screw as shown in the illustration; and which 
also acts asa slow motion. The worm cut on periphery of stage 
has 360 teeth, equal to.single degrees, and the tangent screw- 
head is graduated to sixty, so that each division reads to one 
minute. The tangent screw can be thrown in or out of connec- 
tion, as required. The above is common to both stages. The 
second stage, as shown in the illustration, is also furnished with 
a sliding object carrier, and with micrometer screws in two 
directions for the direct measurement of object without any 
reference to magnification. The.screw threads are one-half 
millimeter, the heads being graduated to 250, so that each 
division reads to two microns. Again, by vernier, to tenths, 
equaling one-fifth microm. At the side of limb there is a scale 
reading to half millimeter; and the slow motion screw-head is 
graduated to 300, each division equaling one micro. The prism 
below fitting in the sub stage has a graduated circle of degrees, 
and a spring catch at each 90°. The prism at the lower end of 
the body-tube has a revolving movement by lever of 90°, and 
can be removed to the side by a slide similar to the “* Wenham 
Binocular prism.” . At the lower end of the tube there is a 
Klein’s Quartz plate and also a centering nose-piece. There is 
a goniometer eye piece with crossed spider line, a Nichol’s 
prism, and a cal-spar plate. The fitting is made adjustable, for 
if the cal-spar is not cut in the proper direction, the cross can 
not be placed in the center of the field without being slightly 
tilted. 
In working, to change from polarized to ordinary illumina- 
tion, the prism below the stage can be turned aside, leaying the 
wide angle condenser in position; or the whole sub-stage can be 
turned aside, which movement is supplimentary to swinging on 
axis in the center with the object on the stage. When the con- 
denser is not required there is a supplementary sub-stage for 
the lower prism, so that the prism can be used close to the ob- 
