268 THE AMERICAN MONTHLY [Sept., 



A cordial vote of thanks to Mr. Emery for 14 years service as cu- 

 rator was moved by the president, and carried with applause. 



The usual announcements were then made and the proceedings 

 terminated. The next ordinary meeting to be held on Friday, 

 September 15, but the rooms to be open on the first and third 

 Friday evenings in July and August for conversation and exhibi- 

 tion of specimens. 



NEW PUBLICATIONS. 



Theorie der Opiischen Instrumente nach Abbe. Von Dr. Siegfried 

 Czapski. pp. 292. Breslau : Edward Frewendt, 1893. 

 As would be exi)ected, this volume deals with the mathe- 

 matics of optical instruments, more especially the construction 

 of lenses both simple and compound. The author has had 

 practical experience in the optical works of Zeiss, in Jena, which 

 has prei)ared him for the preparation of this most excellent vol- 

 ume on the science of optical instruments The numerous mathe- 

 matical formuhe are, in many cases, illustrated by drawings- 

 The work is divided into nine chapters or parts. The first deals 

 with geometrical optics, the second with the geometrical theo- 

 ries of optical pictures including a discussion of the various 

 standpoints for the treatment of the question. Then comes the 

 use of light and its character and effect, a discussion of spherical 

 aberration, acromatism, prisms and prism systems. This is 

 followed with an exhaustive discussion, of the principal kinds 

 of optical instruments. In fact, all of the principles of optics 

 are brought out and demonstrated mathematically. This ren- 

 ders the book of value and it is to be regretted that there is not 

 an English translation although it is presumable that those for 

 whom the book is especially written will find no difficulty in 

 reading the original. The appearance of this volume is a step 

 forward and its effect will undoubtedly be felt in the demand for 

 microscopes and lenses constructed in the best manner. It will 

 teach the people the principles employed in the manufacture of 

 their instruments, which will cause the makers of lenses to put 

 forth their best work. Although the facts stated were for the 

 greater part published, there appears to be no other volume in 

 which all of these important and difficult questions are brought 

 together and explained so satisfactorily as in this one. 



