ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
541 
before a dangerous strain can be put upon the frame, the head turns 
harmlessly upon the pivot. 
An earlier form of the instrument was described by Dr. Flint in 
1892.* Another inventor of a rotatory disc was Dr. Taylor, whose device 
was noticed in our Journal. f 
For the illustrations to this abstract we are indebted to the courtesy 
of the editor and publishers of the Scientific American. 
HjIger, H. — Das Mikroskop und seine Anwendung. (The Microscope and its 
Application.) 
8th edition, by C. Mez. Berlin (Springer), 1899, 8vo, 335 pp. and 326 figs. 
Leiss, C. — Die optischen Instrumente der Firma It. Fuess, deren Beschreibung, 
Jnstirung, und Anwendnng. (The optical instruments of Messrs. R. Fuess : their 
description, adjustment, and application.) 
Leipzig (Engelmann), 1899, 233 figs, and 3 pis. 
(3) Illuminating- and other Apparatus. 
Kohler’s Apparatus for Uniform Illumination 4 — The object of this 
apparatus, manufactured by Zeiss, is to provide an easily made cheap 
arrangement for obtaining uniform illumination from the spectrum itself. 
It is therefore independent of light -filters. 
Figs. 135, 136 give the section and ground plan. D E F G is a 
Fig. 135. 
board, about 60 cm. long, on which the apparatus is placed. It is about 
2 cm. thick, and is made of three thin boards glued together cross-grained 
to prevent warping. The side D E is 12 cm. long, and has a levelling 
screw S x ; at the end F G, 40 cm. long, are two other levelling screws. 
These screws, which are 6 to 7 cm. high, allow not only levelling but 
considerable adjustment in height. On this base-board is placed the 
sector H J K L, consisting also of three thin boards glued together 
cross-grained. K L is an arc, capable of being rotated about the pivot s 
in H J. In order to separate the planes of the sector and base-board, the 
pin s is passed through a little disc, and two similar discs are placed at 
* Proc. Ame.r. Soc. Micr., xiii. (1892) pp. 54-8 (1 pi.), 
t Tom. cit., p. 30 (1 pi.) ; Journal R.M.S., 1892, pp. 862-3 (fig. 94). 
t Zeitschr. f. wiss. Mikr., xvi. (1899) pp. 1-29 (5 figs.). 
1899 2 o 
