Fig 
538 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
seen in fig. 77, wbicli acts upon the lever a fitted to the micrometer 
screw. On the glass plate of the camera four squares are etched, so 
that it can be simultaneously 
used as a transparent and as a 
ground glass plate. The total 
length of extension of the 
camera from Microscope stage 
to glass plate amounts to about 
85 cm. 
7 
(5) Microscopical Optics and 
Manipulation. 
Theory of Optical Instruments."' 
— The appearance of this hook by 
Dr. S. Czapski will be welcomed by 
all microscopists who possess the 
mathematical knowledge necessary for 
the due appreciation of Prof. Abbe’s 
theories on the formation of the 
microscopic image. 
The book is really an abstract of 
the articles which the author contri- 
buted to Prof. Winkelm aim’s ‘ Hand- 
buch der Physik.’ It is not, however, 
a text-book of optics, as only those 
points are dealt with at length which, 
in the author’s opinion, are not to be 
found adequately treated elsewhere. 
The main object of the book is to 
demonstrate the advance s which have 
been made in our understanding of 
the behaviour of optical instruments 
owing to the observations and theories 
of Abbe. The phenomena of diffrac- 
tion and the famous diffraction theory 
(ihe “ Abbe theory ” proper), however, 
are not discussed in this book, but are 
reserved for a subsequent work. 
After a preliminary chapter deal- 
ing with the general principles of 
geometrical optics, there follows a 
full discussion of the Abbe theory of 
the formation of images. This is 
succeeded by a chapter treating of the 
theory of spher’cal aberration and the 
conditions necessary for its compen- 
sation (achromatism). Prisms and 
* ‘ Tlieorie der Optisehen Instrumente nacli Abbe,’ Breslau, 1893, 8vo, 292 pp., 
91 figs. 
