ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
819 
practical plan for the construction of photo lenses can be laid down, and 
they cannot fail to admire the skill and patience that has given us the 
good lenses we possess, without clearly understanding the numerous 
conditions they must satisfy. Though the work deals mainly with the 
construction of photo lenses, it will prove itself as useful for the combina- 
tion of any other kind of lenses, as the formation of images and the correc- 
tion of chromatic and spherical aberrations, astigmatism, and diaphragms 
have been masterly treated. Actinism, of course, need not be taken 
into account in telescopic and microscopic lenses. 
The work is preceded by a valuable list of the principal optical works 
that have appeared since Newton in English, French, German, and 
Italian, including fragmentary dissertations contributed to the learned 
societies, with annotations by the author. Whilst it numbers some 200 
works on general optics, only six or seven refer specially to photography. 
First among these are Petzval’s, published in 1843, 1857, and 1858. 
Dr. H. Zinken, Yoightlaender’s son-in-law ; Dr. Lorenzo Billotti, 
Schiaparelli’s assistant at Milan ; and Prof. Seidel, Steinheil’s friend, at 
Munich, also contributed considerably to the perfection of photographic 
optics. Still, nothing complete and easily understood appeared until 
the work under notice was called forth by Prof. W. Vogel in Berlin to 
form a supplement to his new ‘ Handbook of Photography.’ 
It is unfortunate that most of this valuable information is in German. 
The present complete treatise, however, will no doubt soon also appear 
in an English dress. Meanwhile I shall be pleased to help those who 
may desire to know something more of the practical rules and formulae 
developed by the author, if the editor will afford me space. Dr. Hugo 
Schroeder possesses the rare advantage of being a linguist and practical 
optician, as well as a mathematician, and this advantage enabled him to 
simplify much that was hitherto obscure, and to bring together informa- 
tion that was scattered about in many inaccessible writings. He dissects 
all the lenses in actual use, and shows on what principles they have been 
constructed, and how they can be still further improved.” 
(6) Miscellaneous. 
New Edition of Carpenter on the Microscope.* — We are glad to 
be able to call attention to the new (seventh) edition of the late 
Dr. Carpenter’s well-known work on the Microscope. Dr. Dallinger 
has been engaged on this work for a considerable time, and has devoted 
much attention to it. When the last edition of this work was published 
the new era in microscopical optics had just opened ; now, ten years 
later, it is necessary to give a full account of the work of Prof. 
Abbe. The consequence is that Dr. Dallinger has had to completely 
rewrite the first seven chapters. These, he tells us, “represent the 
experience of a lifetime, confirmed and aided by the advice and practical 
help of some of the most experienced men in the world, and they may 
be read by any one familiar with the use of algebraic symbols and the 
* ‘ The Microscope and its Revelations,’ by the late W. B. Carpenter. 7th ed., in 
which the first seven chapters have been entirely rewritten and the text throughout 
reconstructed, enlarged and revised by the Rev. W. H. Dallinger, LL.D., F.R.S., &o. 
xviii. and 1099 pp., 21 pis., and 800 wood engravings. London, 1891. 
