304 J. H. B. L. on a Mechanical Finger for the Microscope. 
ArT. XXXI.—On a Mechanical Finger for the Microscope; by 
JOH Bei 
In the Journal of May, 1866, there is a description and wood- 
cut of a mechanical finger, by Mr. H. L. Smith. 
There are few naked eyes, or ordinary hands, that can select, 
from a mass, one of the smaller diatoms; and the engraving in 
the Journal was seized upon, at once , by the writer, as afford- 
a promise of relief in the patient labor that had so often tes 
ta both his eye and hand. It was his “gh fortune to be with- 
reach of one of the instruments. It was a great help, no 
dante, and, fier acquiring “the knack,” Hes was possible to use 
it. But it wanted solidity, and the writer ventured to think 
that it might be made firmer, if constructed with fewer parts 
and joints. It was a capital idea, however, usefully poe 
but not beyond improvement: so an improvement, a 
thought, was put on paper, and sent en Mr. Joseph ven tisitege 
the well known optican of Philadel 
Putting aside Be Hoth the improvement and the original, Mr. 
duced what seems to be very near perfecti 
The microscope, in the writer’s possession, is one of Mr. Zent- 
mayer’s large first class ones, though the finger can be adapted 
to any other. There pleces : ‘or an independent 
stage, that ve her call the diatom stage, supported, 
above the prin stage, upon a tube that sa into : slee 
attached to a ovate (fig. 2), that fits seg e sub-sta, 
tube of the diatom stage is passed t opening a the 
Really: stage into the sleeve, as fot in the ing, 
S, with an ivory button, B, is attached to the diatoha stage, as 
at in fig. 4, which steadies the oe as it is moved by hand 
diffe 
ig 3 shows the third piece of et apparatus, or, gic! , the 
only piece, so far as the finger is concerned; the other three 
ep being necessary to hold the slide containing the ‘aiatoms 
ut having, otherwise, nothing to do with the finger proper 
The drawing is of full size A is a clamp secured to the pria- 
cipal ae by the jaws M and the movable plate L, which is 
tightened by the set screw D. The cylinder g 
' the clamp resting on the shoulder It turns horizontally 
: when not fixed by the set screw F, whose point presses in the 
_ groove drawing. The steel B, surrounded by 
a «: spring, which is nt seam but which can be readily 
