ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
463 
MICROSCOPY. 
a. Instruments, Accessories, &c.* * * § 
(1) Stands. 
Leitz’s Microscopes.f — M. E. de Wildeman describes several of the 
Microscopes supplied by the tirm of Leitz. In many cases the same 
stand can be obtained either with the Continental horse-shoe base or 
with the English tripod. 
One large model is inclinable, and has a horse-shoe base. It is 
provided with coarse- and fine-adjustment, and with a draw-tube with 
a scale indicating the total length of the tube. The circular stage is 
movable, and can be centered. Beneath the stage is the Abbe illumi- 
nating apparatus, with iris- diaphragm, which can be displaced laterally. 
There is also beneath the stage a cylinder-diaphragm, in which is 
another iris-diaphragm. Another model is very similar, but with tripod 
base, and without the cylinder iris-diaphragm. 
The model II b is intended for institutions and for students. It is 
provided with both fine- and coarse-adjustment so that high-power 
objectives can be used. The illuminating apparatus is much simpler 
than in the preceding models, and consists of a cylinder carrying above 
a lens, and below an iris-diaphragm. 
Use of Ordinary Binocular for Dissecting. J — Dr. J. Tatham makes 
use of the ordinary binocular for dissecting, by the device of attaching 
to the rackwork substage a brass ring carrying a supplementary stage. 
For dissecting, the Microscope is placed in the vertical position, and 
the low-power objective is racked down through the aperture of the 
principal stage until focused upon the object lying on the supplementary 
stage. 
(3) Illuminating- and other Apparatus. 
Method for the Exact Adjustment of the Nmol's Prisms.§ — Dr. E. 
Weinschenk gives the following method for adjusting the Nmol's prisms 
of the Microscope : — 
A doubly refracting crystal between two nicols shows no interference 
colours during the rotation of one of the nicols, if one of its directions 
of vibration is exactly parallel to the direction of vibration of the other 
nicol. For the application of this principle to the adjustment of the 
nicols a crystal is required which allows its directions of vibration to 
be adjusted exactly parallel to the cross-wires, and gives lively inter- 
ference colours of a low order. These properties are possessed by 
quartz which occurs in water-clear needles 5 to 7 mm. long and 
0*05 to 0*15 mm. thick. Such a needle is imbedded in Canada balsam, 
* This subdivision contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) Illu- 
minating and other Apparatus; (4) Photomicrography; (5) Microscopical Optics 
and Manipulation; (6) Miscellaneous. 
+ Bull. Soc. Beige de Micr., xxii. (1896) pp. 74-7. 
X Journ. Quekett Micr. Soc., vi. (1896) pp. 206-7. 
§ Zeitsch. f. Krystallogr. u. Min , xxiv. (1895) p. 581. See Zeitschr. f. Instrumen- 
tenk., xvi. (1896) p. 188. 
