PREFACE. 



THE nomenclature of a science is one of the most im~ 

 portarit portions of its structure, and the Science of 

 Instruments requires a good dictionary as a basis. It 

 is believed that a concise definition of each instrument, 

 together with illustrations of the most important types, 

 will be of real service to scientific men and the industry. 



This book is not only a means of information and 

 reference respecting scientific instruments of every 

 description, but also exhibits the great variety of such 

 instruments that are produced in Great Britain. Key 

 numbers corresponding with a numbered list of manu- 

 facturers are attached to the dictionary descriptions. 



The British Optical Instrument Manufacturers' Asso- 

 ciation, under whose auspices the book is issued, is com- 

 posed of the leading Optical Instrument Manufacturers 

 of Great Britain, the names of whom will be familiar 

 throughout the world. From these houses have emanated 

 in years gone by the original types of which the present- 

 day highly developed, and often complex, instruments 

 are the outcome, and these houses have throughout 

 maintained that high standard of excellence and fine 

 working quality for which British instruments are 

 famed. 



The British Optical Industry succeeded in meeting 

 the increased requirements of the War to an extent 

 that was not considered possible, and to-day with greatly 

 enlarged factories, equipped with mechanical machinery 

 of the most suitable and modern description, with supplies 

 of optical glass constantly increasing in quality and 

 variety, and aided by a Research Association adequately 

 financed, it is in a position to give its supporters a service 

 in brains and goods that has never before been available. 



The Association issues this book with the full assur- 

 ance of the ability of its members to meet the demands 

 of all who are interested in the promotion and mainten- 

 ance of the supremacy of the British Optical Instruments, 

 and invites their confidence and support. 



September 1919 



