i66 SCIENCE PROGRESS 



whowere assisted bythe Standing Committee on Glass and Optical Instruments, 

 to the deficiency of books in the English language dealing with geometrical 

 and technical optics. Accordingly they authorised, in the interests of the 

 scientific and industrial development of optics, translations of Dr. Gleichen's 

 theory of modern optical instruments, and Dr. von Rohr's theory of optical 

 instruments. The translation of the former work was first published by the 

 Stationery Office for the Department of Scientific and Industrial Research in 

 191 8. On the recommendation of the Standing Committee on Glass and 

 Optical Instruments, Mr. R. Kanthack was invited to translate Dr. von 

 Rohr's book. 



Based upon the fundamental geometrical laws of light, this work deals 

 with the methods of computation of optical systems. It embodies the 

 exhaustive researches made by eminent men of science, amongst whom 

 British investigators occupy an important place. The translator says in his 

 preface that the inception of the work with which he was entrusted repre- 

 sented to him far more than the preparation of an English version of a work 

 which may be regarded as the most valuable modern elucidation of the 

 principles of constructive optics. He felt convinced, from personal observa- 

 tion as well as the testimony of others competent to express unbiassed 

 opinions, that the achievements of German workshops and the sympathetic 

 development of the cognate theoretical studies could not be accounted for 

 solely by education and by State assistance. In a very large measure the 

 success of the Germans as opticians is the outcome of a far-seeing policy, 

 requiring for its conception something of the imagination and courage of an 

 idealist. The famous Zeiss works at Jena and its history furnish no more 

 than a somewhat overshadowing example of a widespread and single-minded 

 association of scientific investigation with workshop practice and industrial 

 aims. It is not enough to equip workshops with all the best that modern 

 technique and organisation have to offer, and to secure the services of the 

 best available scientific brains for carrying out the industrial programme of 

 an establishment, leaving to the savants all scientific effort which has no 

 direct bearing on production. The hope which the translator cherished when 

 he undertook the work is that the book may appeal to the imagination of 

 British opticians, and help to stimulate further the rising spirit of scientific 

 enthusiasm which looks beyond the immediate needs of successful production. 



This book is not one which can be subjected to criticism. It is, in fact, 

 the embodiment of all that is known of theoretical optics in relation to those 

 parts of the subject with which it deals. It has been studied by a competent 

 committee, and at their instigation the translation has been produced. 



The book covers the whole range of matter as indicated by its title, and 

 each section of it has been dealt with by an acknowledged authority on 

 each branch of the subject. The translator has been extraordinarily careful 

 in eliminating errors, and the mathematical part has been most efficiently 

 dealt with. 



There is an author's index as well as a general index to the work, and 

 this provides a practically complete bibliography of the subject. The list 

 of symbols also is a great aid to a reader, as by its means the mathematical 

 formulas can be interpreted without difficulty. 



The book may be regarded as indispensable to anyone who is studying 

 the theory of optical instruments, either as to its theoretical side or in its 

 practical application. J, E. B. 



