ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
245 
MICROSCOPY. 
A. Instruments, Accessories, &c.* 
(1) Stands. 
Stands and Optical Equipments.! — In an editorial article figures of 
two stands are reproduced from the latest catalogue (No. 20) of Reichert 
of Vienna. General remarks are made concerning oculars, and a list is 
given of the numbers, focal lengths, amplifications, and 
prices of the oculars of various firms. The apertures, 16 
focal lengths, and prices of achromatic, apochromatic, and 
semiapochromatic objectives, both dry and immersion, are 
quoted from catalogues and compared. 
C3) Illuminating: and other Apparatus. 
Ocular-Dichroiscope.J — Herr C. Leiss figures a com- 
bined eye-piece and dichroiscope (fig. 16), with the aid of 
which the two colours shown by crystals of microscopic 
dimensions may be seen side by side, and so directly com- 
pared. This is an improvement on the usual method of 
rotating the polariser or the crystal. A rectangular dia- 
phragm is placed behind the calcite prism I\, as in the 
ordinary dichroiscope. 
(4) Photomicrography. 
Method of Projecting a Micrometric Scale upon a Microscopic 
Specimen. — The accompanying figure (fig. 17) illustrates the apparatus 
■contrived by Prof. A. E. Wright for measuring and counting microscopic 
objects, described on p. 182, and exhibited at the March meeting of the 
Society. 
The window-pane and the projection-scale (which is etched upon a 
piece of plate glass) are shown in optical section at A and B respectively. 
The method of suspending the scale, so that it may be at right angles to 
the beam of light which is thrown upon the microscopic mirror, is shown 
at C. The scale is allowed to tilt forward until, as in medallions A and 
B, an equal number of vertical and horizontal divisions appear within 
'the microscopic field. The minified image of the projection-scale, which 
is superposed upon the microscopic object, is shown in optical section at 
G. The adjustment of the condenser, which is essential to the super- 
position of the minified image upon the microscopic specimen, is most 
easily achieved by first focusing the microscopic objective upon the 
microscopic specimen, and then, while keeping this plane under observa- 
^ * Tliis subdivision contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) Illu- 
minating and other Apparatus; (4) Photomicrography; (5) Microscopical Optics 
.and Manipulation ; (6) Miscellaneous. 
t Zeitschr. f. angew. Mikr., ii. (1897) pp. 351-60 (2 fig?.). 
X Op. cit., iii. (1897) pp. 5-6 (1 fig.). 
