ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
113 
which the Jena glasses were extensively used ; the newest of these was 
the “ Concentric” objective for landscape and architectural photography, 
consisting of tvvo symmetrical double-lenses. Watson and Son, besides 
astronomical and measuring instruments, exhibited photographic and 
projection apparatus and Microscopes. Amongst tbe latter was shown 
the Van Heurck Microscope for work with high magnification, one of the 
peculiarities of which is the special draw-tube which allows of the use 
of the German as well as the English tube-lengtb, according as the 
objective to be used is corrected for one or the other. The firm of Beck 
also exhibited a collection of Microscopes. 
Other European nations were well represented in the department of 
Microscopy by the firms of Nachet, Keichert, and Koristka. 
Amongst American exhibits tbe Gundlacb Optical Co. showed their 
photographic objectives and Microscopes; and the Bausch and Lomb 
Optical Co. a large collection of their Microscopes, microtomes, and 
pliotomicrographic apparatus. A peculiarity in the Microscopes of the 
latter firm was a hemispherical diaphragm intended to replace the Zeiss 
iris-diaphragm. 
/3. Technique.* 
Practical Methods in Microscopy.! — This is an elementary manual 
of microscopical manipulation intended to guide such as have little or no 
previous acquaintance with the instrument, or the methods of examina- 
tion and preparation of objects. It deals firstly very briefly, but perhaps 
sufficiently for an absolute beginner, with the phenomena of refraction, 
the formation of optical images, aberration, and so forth, followed by a 
description of the compound Microscope and its chief accessories, drawing 
instruments, microtomes, &c., polarized light having a short chapter to 
itself. Manipulation and the examination, preparation and mounting of 
specimens necessarily take up the major part of the work, and the pages 
devoted to making sections of vegetable and animal tissues, rock sections 
without a lapidary’s wheel, and the cultivation and staining of bacteria, 
are up to date and quite as full and exact as is required by the class of 
student for whom the book was specially written. No mention, however, is 
made of the freezing process, which is rather an oversight considering the 
great convenience of such instruments as the Cathcart, and particularly 
Jung’s automatic ether microtome, to those who do not devote themselves 
almost entirely tc section-cutting, as, after all, the complicated celloidin 
and paraffin processes are only requisite for serial sections, or where the 
material necessitates continual internal and external support during the 
whole time it is under treatment. It is perhaps superfluous to state that 
the now indispensable chapter on photomicrography is not forgotten. 
The work is illustrated with the usual figures, and also by a series of 
process plates from photographs done with a low power. It is well 
printed, and commendably free from errors, typographical or otherwise, 
but in the examination of human blood (p. 79) the white corpuscles are 
* This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses; (2) Preparing Objects ; (3 'j Cutting, including Imbedding and Microtomes ; 
(4) Staining and Injecting; (5) Mounting, including slides, preservative fluids, &c. ; 
(b) Miscellaneous. 
t By Ckas. H. Clarke, A.M.. Boston, U.S., and London, 1894, 211 pp. 
1895 • I 
