387 



NOTICES OF NEW BOOKS. 



The Theory of Modern Optical Instruments. A Eeference Book for 

 Manufacturers of Optical Instruments and for Officers in the Army 

 and Navy. By Dr. Alexander Gleichen. Translated from the 

 German by H. H. Bmsley, B.Sc, and W. Swayne, B.Sc, with an 

 appendix on Range-Finders. Published for the Department of 

 Scientific and Industrial Research by His Majesty's Stationery 

 Office, 1918. 



The Committee of the Privy Council for Scientific and Industrial 

 Research realized at an early stage the necessity for rendering assistance 

 to the optical instrument making industry ; and it was suggested by 

 their Advisory Council, assisted by the Committee on Glass and Optical 

 Instruments, that one way of doing this lay in the translation and 

 publication of certain foreign works. 



The volume here noticed has been prepared under the direction of 

 an Editorial Committee. The Committee have not been asked to review 

 the terminology and the use of symbols adopted by the translators. 

 For this, by raising the whole question of nomenclature in optics, would 

 not only have caused a serious delay in the appearance of the work, but 

 would have raised difficult and far-reaching problems which could not 

 at the present moment receive the attention they deserve. 



The text of the original has been closely followed, with certain 

 exceptions, to which reference is made in the translators' preface. 

 During the last decade many noteworthy improvements have been made 

 in the manufacture of optical instruments which have not been 

 published collectively. The object of this book is to remedy this 

 deficiency. In order to make the matter clear to the non-technical 

 reader a section on General Theory is included, dealing with information 

 on elementary geometrical principles, and having particular reference 

 to the dioptric conception developed by Guhlstrand and since further 

 elaborated. 



Dr. Gleichen has divided his work into two portions. In the first 

 he has given a very clear resume of the more important laws of refrac- 

 tion at spherical surfaces, and of the formation of images by lenses and 

 their combinations. The second portion deals with the direct application 

 of these laws to the particular instruments described therein. Both 

 portions are written so as to be intelligible to the more elementary 

 student, who may not possess the advanced mathematical training 

 necessary for the understanding of more difficult treatises, and, moreover, 

 in such a manner as to permit of ready application. 



2 D 2 



