February 27, 1919 



NATURE 



ABBE REFRACTOMETER 



For the rapid measurement of 

 the refractive indices and 

 dispersions of liquids and 

 solids from 1*3000 to 17000. 



Delivery in two weeks from receipt of order. 

 Descriptive booklet post free on application. 



Just published. 



The Refractive Indices of Essential Oils. 



1 5s. Ad. post free. 



ADAM HILGER Ltd., 

 75a Camden Road, London, N.W. 1. 



Telephone Numbers : NORTH 1677- 



Teleeraph^c Addr, 



■SPHERICITY. PHONE. LONDON.' 



W. OTTWAY & Co., Ltd. 



(Established 1700) 



Orion Works, Ealing, London, W. 5. 



Manufacturers of all types of Astronomical, 

 Scientific, and Optical Instruments. 



ELECTRO-CULTURE SET 



in weather-proof hut. 



Side of 



roof 

 removed 



to show 

 interior. 



A Weather-proof lead-out. C Spark gauge. 

 B Inner terminal of above. D Automatic switch & fuses. 

 Pamphlet on application to 



HARRY W. COX & CO., Ltd. 



42, 44, 46 Wigmore Street, London, W. 1. 



