THE MIcROSCOPE. 369 
pressure upon it; it is hampered in no way; it may be placed 
in position or removed in a moment; or, if it needs to be 
fastened in place when the microscope is turned down hori- 
zontally to draw the object with the camera lucida, a light spring 
may be swung above it. This admirable device the majority of 
dealers use on their higher grade stands, either in Mr Zent- 
mayer’s form or modified to suit the exigencies of the case. 
There is, however, no better form than Mr Zentmayer’s original 
one. With it investigations may be made in any department, 
except certain very delicate observations only possible with a 
mechanical stage. If the beginner’s stand has Mr Zentmayer’s 
glass stage plate, he may feel entirely contented. 
On some of Mr Zentmayer’s stands he uses a narrow strip or 
bar of glass, held in movable position by spring clips, the slide 
resting against the upper edge of this, and being moved lateral- 
ly by the fingers, and vertically by moving the narrow bar, the 
slide retaining its place by its weight. This is commendable 
because the clips can never come in contact with the slide, but 
it is not an enviable addition to any stand. To move the slide 
laterally after it has been moved vertically, the fingers must be 
shifted from the glass bar to the slide, and while that is being 
done, a living creature would be out of the field, probably forever, 
since microscopic animals are usually like time and tide and the 
rail-roads, they wait for no man to shift his fingers. This is the 
least convenient and the least commendable of all of Mr Zent- 
mayer’s many valuable contributions to the microscope. 
Other opticians make a stage of glass which bears on its up- 
per surface a metal slide holder movable by the fingers, the slide 
being held in place by spring clips. This is not objectionable, 
as the clips are not disturbed during the manipulations of the 
slide, the carrier and all moving together. On Messrs Bausch and 
Lomb’s larger stands, this arrangement has a smooth and pleas- 
ant motion; the spring clips may be turned back out of the way, 
and the distance transversed by the slide carrier is ample. 
There are, or have been, many forms of movable stages, but 
most of them have disappeared. Here, as elsewhere, there has 
been a survival of the fittest. Occasionally, on the less recent 
stands, but rarely even there, a lever stage may be seen. This 
consists of two thin brass plates, a long lever piercing the upper 
one and entering the lower by means of a ball and socket joint, 
