1877.] Microscopy. 697 
- past. The same may be said of the United States, though increased at- 
tention has lately been paid to the planting of new and the preservation 
of old forests. 
MICROSCOPY.! 
Tae New MECHANICAL FINGERS. — Several new devices for pick- 
ing up and arranging diatoms, Polycystina, and other small objects have 
recently been described, the chief peculiarity of which consist in sup- 
porting the object from the substage, while the instrument is supported 
from and moved by the stage which usually bears the object-slide. By 
unaccountable oversight it was not stated that this expedient was the 
chief peculiarity of Mr. Zentmayer’s mechanical finger, which was con- 
trived in 1869, published in different journals early in the following 
. year, and advertised and sold as a regular article of manufacture ever 
since. In the May number, 1870, of the Journal of the Franklin Insti- 
tute, a cut is given of Zentmayer’s invention, in which the finger is 
fastened to a pillar clamped to the upper plate of the mechanical stage 
of the microscope, while the substage is prolonged through the opening 
of the stage for the purpose of supporting the object. In the accom- 
panying description Mr. Zentmayer explains that it was his object to 
utilize such movements of a first-class stand as were not essential for 
other operations connected with the use of the finger ; that by attaching 
his apparatus to the mechanical stage he obtained sliding horizontal 
movements with a firmness and range not otherwise attainable ; and that 
for the low powers employed a plain stage supported from the substage, 
and projecting slightly above the stage, was all that was required for 
holding the object and would give the necessary vertical movement to 
it. Mr. Zentmayer makes a special accessory to the substage for carry- 
ing the object, and a vertical adjustment to the finger itëelf; while sub- 
sequent experimenters have supported the object on the paraboloid or 
some other piece of common apparatus, and have simplified the finger 
by dispensing with a vertical adjustment, in both cases saving complica- 
tion and expense at some loss of efficiency. 
A Mopirication or Wenuam’s REFLEX ILLUMINATOR. — The 
very ingenious and interesting reflex illuminator of Mr. Wenham was 
designed to avoid direct illumination by passing light into the slide at 
such an angle that it would be totally refiected instead of passing into 
air above the slide. With dry objectives, of any angle, this illumination 
would necessarily be exclusively reflex, since no light could pass directly 
to the objective; and with immersion objectives of angular aperture not 
greater than that corresponding to one hundred and eighty degrees dry, 
the result would be practically the same, as the light, after passing 
through a balsam-mounted object, would reach the lens at an obliquity 
greater than that of its extreme capacity for image-forming rays. But 
1 Conducted by Dr. R. H. Warp, Troy, N. Y. 
