ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
563 
the disc. The whole apparatus is strongly constructed of iron and 
brass. 
Box for Coiouring-Keagents.* * * § — This box has room for ten stoppered 
bottles for the usual colouring-liquids, imbedding material, &c. The 
pipette bottles are for methylen-blue, fuchsin, eosin, alcohol, and xylol. 
There is also a glass for Canada balsam. A space is also left for 
platinum wire, needles, knife, pipettes and other instruments. 
Simple Thermostat for Microscopes of different Construction.!— 
This apparatus is so constructed that the Microscope can be placed in 
the heating chamber from behind. The box is large enough to take all 
ordinary stands. 
(4) Photomicrography. 
Optical Works of C. P. Goerz in Schoneberg, Berlin.]: — Herr J. 
Goedicke describes a visit to these works, in which the well-known pho- 
tographic objectives, the double anastigmatics, are produced. The firm 
now employs 250 workers. The manufactory consists of a large square 
building of six stories. In the basement, the first process consists in cut- 
ting up the blocks of oj)tical glass into plates of exactly determined thick- 
ness. From these plates square pieces are cut out, to which an approxi- 
mately circular form is given by cutting down the edges. Then follows 
the grinding down with sand on rotating brass forms, which have a 
special curvature for each lens. The rough lens thus formed is some 
tenths of a millimetre thicker than it must be in its completed state. 
This rough lens is then submitted to fine grinding and polishing with 
gradually finer emery. For each curvature a very exact pattern glass is 
produced, which must be exactly filled by a correctly ground lens. 
From time to time during the grinding the lens is fitted into the pattern 
until at last no Newton’s rings are observed in any position. For the 
double anastigmatic six lenses are required. These are cemented 
together with Canada balsam so as to form two symmetrical glasses. 
They then pass from the hands of the optician to those of the mechanic, 
to be fitted into the frames. Finally, they are submitted to rigorous 
optical tests, and if found faultless are engraved with a number and the 
name of the firm. 
Practical Photomicrography.§ — Dr. W. C. Borden gives a detailed 
account of the apparatus and method which, after much experience, he 
has adopted in photomicrographical work. The Microscope is used in 
the upright position, while the camera is hung on a rackwork attached 
to an upright placed on the right of the Microscope. Both the upper 
and lower ends of the camera are movable on the rackwork. As illu- 
minant the acetylene burner is recommended as te the best artificial light 
now obtainable for use in photomicrography.” A good filter for this 
light is a solution of 10 grin, of potassium bichromate in 200 ccm. of 
water contained in a trough 3 cm. wide. The author gives elaborate 
instructions for the adjustment of the apparatus, &c. He recommends 
* Zeitschr. f. ang. Mikr., ii. (1896) pp. 34-5. 
f Centralbl. f. Bakteriol. u. Parasitenk., xviii. l te Abt., No. 11. See Zeitschr. f. 
ang. Mikr., ii. (1896) p. 108. 
X Central-Ztg. f. Optik u. Meek., xvii. (1S96) pp. 151-3. 
§ Amer. Mon. Micr. Jouru., xvii. (1896) p. 193-208. 
