266 THe MiIcroscopr. 
Zentmayer’s “ Centennial,” there is a revolving platform to which 
the pillars are attached, and whose bevelled and silvered edge is 
graduated in degrees for the measurement of the angle of aper- 
ture of objectives. Nothing of the kind is applied to the cheaper 
stands, but even without it the aperture may be measured with 
approximate correctness. 
THE SUPPORPING PILLARS. 
In some stands the single pillar is a straight cylindrical rod 
extending from the foot to the arm, to which it is attached at its 
upper end and which in its turn bears the body. This arrange- 
ment is common on French and German stands, which are there; 
fore called the continental model. It necessitates a low instru- 
ment and a short body-tube, since the microscope must be used 
in a vertical position. This model is strongly advocated by some 
American microscopists whose backs must be like the one that 
Charles Dudley Warner wished for when he hoed his veget- 
ables, as detailed in “ My Summer in a Garden,” for they must 
be of cast iron with a hinge in the middle. If the purchaser is 
wise he will not buy a stand made on the continental model. If 
he must use his microscope in a vertical position he can sit ona 
high stool with the instrument on a low table, and he will then 
get the back ache and a crick in his neck almost as soon as by 
using a stand with a rigid pillar. It seems better to put the 
hinge in the pillar so that the instrument may be inclined at a 
convenient angle, and to keep your vertebral column as Nature 
made it. 
In the best and most complete stands where expense is not, 
considered, the pillars are two, the arm swinging between them. 
with a milled head on the outer side of each to clamp the in- 
strument at any angle of inclination. This is an admirable con-. 
trivance not found on the smaller and cheaper stands. It obvi- 
ates the trouble sometimes occasioned by the wear of the joint, 
and its consequent leoseness. In the least elaborate models the 
joint not only has no adjustment for wear, but the pillar is often, 
single. There is no rule for this, however, among American 
manufacturers, as most of them make stands with either single 
or double pillars. To me the double pillars have always seemed 
preferable, although I have no very valid reason to give, except. 
that an instrument perched at the summit of a single stem seems 
so insecure that I usually feel like steadying it with my hands. 
