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SUMMARY OF CURRENT RESEARCHES RELATING TO 
to or illustrated, but there is a final chapter, in the form of a translation 
of a paper by Dr. S. (Jzapski, which gives a suggestion for the possible 
enlargement of the practical N.A. of homogeneous lenses, which gives us 
the possibility of advancing to ‘DO or beyond it without the employment 
of the dense flint and high refractive media needed by the lens we have 
referred to. Tliis communication has already appeared in English in 
this Journal, and indicates clearly the value of true monochromatic light 
which may increase a N.A. of 1'40 to l - 75. 
There is a considerable chapter on “ Photomicrograpliie.” This, as 
a matter of course, is excellent, but is not exhaustive nor as specially 
critical in regard to instruments and methods as might bo desired. 
As must inevitably be the case in all general treatises on the Micro- 
scope, the chapter on the preparation and mounting of objects is sug- 
gestive, and, so far as it goes, useful, but inefficient. But the student 
may well be content, for many handbooks are now obtainable wholly 
devoted to the subject. 
In regard to the important question of what a Microscope should be, 
what are its points of excellence, what is indispensable, and consequently 
what should be its general form and detailed construction, we do not 
obtain very definite conclusions. A large array of Microscopes are pre- 
sented in an illustrated form, but they are mostly described, without 
being critically compared. We have, however, a figure of an instrument 
prepared by Messrs. Watson for Dr. Van Heurck, described and illus- 
trated. Wo presume this will be more or less the expression of what 
the author desires in a Microscope. It is no doubt fitted with what are 
intended to be the latest improvements ; but, to begin with, it would be 
held by most experienced workers, especially photomicrographists, that 
the stand is most defective from its form, involving lateral instability, 
and securing such stability as it possesses by weight rather than by 
construction. But this is secondary to the want of perfection in its fine- 
adjustment and the mode of centering in its substage, to say nothing of 
the awkward position of the milled head employed, apparently, in giving a 
fine-adjustment to the substage, and the great thickness of the stage itself. 
The book is well printed, and fairly illustrated; it gives a brief 
history of the instrument it describes, and instructs the reader how to 
use it. It will be of service to many, and throughout gives valuable 
hints, as well as lucid instruction, to those who seek to understand how 
to use to the best advantage one of the most delightful instruments 
employed in the study of nature. 
Text-book of the Microscope.* — This is one of the most practical 
books yet presented to the laboratory student. The aim is to enable him 
to understand his instrument in at least its broader principles, and thus 
to apply' it intelligently to the study of histology. It cannot be doubted 
that there is, chiefly perhaps because of the great variety of subjects 
requiring to be dealt with in the medical curriculum, a deficiency of 
knowledge amongst students as to the principles and the optical laws 
involved in the construction and use of the Microscope. Prof. Gage 
* ‘ The Microscope and Histology, for tho use of laboratory students in the 
anatomical department of Cornell University, by Simon Henry Gage. Part I. The 
Microscope and Microscopical Methods.' 3rd ed. Ithaca, N.Y., 1891, 8vo, 96 pp. 
interleaved, 5 pis., text illust. 
