XXXIV NATURE [SEPTEMBER 18, 1913 
THE HERBERT SMITH | 
REFRACTOMETER 
i 
AWE 
ATTN 
(No. 2 Model) : 
The scale gives the refractive indices with. 
ReeractivelNpex| out calculation to the second place of — 
decimals, and by estimation to the third, 
and the instrument will accommodate any 
faceted stone, however large its size. ~ 
Microscopes and Accessories 
Microtomes and Accessories 
Photomicrographic Apparatus 
Projection Apparatus 
Blood Counting Appliances 
Aplanatic Pocket Lenses 
For Field 
and Theatre 
I Ait 
Prism Binoculars 
ETC. 
Awarded GRAND PRIX at the 
International Medical Congress. 
The Herbert Smith Refractometer, in case complete ‘ 
with accessories and explanatory pamphlet ove » £660 j 
Pamphlet on the Refractometer and its use, particularly for the 
Discrimination of faceted Gem-Stones, which contains complete — 
tables of the physical characters of the Gem-Species and Index 
to their varieties, also the Refractive Index of various liquids, 
by Dr. Herbert Smith, post free, 2/6 
J. H. STEWARD, Ltd. 
Oplicians & Scientific Instrument Makers to the British & Foreign Govts. 
406 & 457 Strand, London. 
ESTABLISHED 1852. 
WATSON’S “SUNICA” PRISM BINOCULARS 
The embodiment of DAINTINESS and PERFECTION. 
To motor, walk, cycle, boat, climb, or make holiday without a Prism Glass means losing a considerable 
amount of enjoyment. A Prism’ Glass reveals hosts of sights that would otherwise be invisible, and adds a 
new charm to everything observed. 
Watson’s “SUNICA” Prism Glass is the right magnification—the compact size—and is the 
always dependable companion that is so much desired. I!’ IS BRITISH-MADE THROUGHOUT AT 
BARNET, HERTS, and that means sound workmanship and quality. 
Sectional Catalogues post free. 
18 BLOOMSBURY SQUARE, W.C. 
(A few doors from the British Museum). 
It has wonderful stereoscopic effect. 
2, A very large angle of field of view—48’—enables 
It is covered with wulcanite of morocco leather a large surface to be embraced. | 
pattern. The optical quality cannot be surpassed. 
Magnification, 6 diameters. Diameter of Objectives, 090in. Height,4'2in. Weight, 22 oz, 
PRICE (post free), with neck sling, and in best solid leather sling case ... £6 O O 
W. WATSON & SONS, Ltd. (7°9837"°), 313 High Holborn, London, W.C. 
Optical Works :—HIGH BARNET, ee 
Branches { 16 FORREST ROAD, EDINBURGH Depots {2 EASY ROW, BIRMINGHAM. 
184GREAT PORTLAND STREET, LONDON, W.C. (7s "SWANSTON ST. MELBOURNE, AUSTRALIA. 
It is waterproof and can be immersed in water. 
It will withstand rough us: 
There are incorporated into 
SPENCER MICROSCOPES. 
many features of practical usability, features which make for convenience 
and comfort in use as well as efficiency and durability, which others do not 
have, and which in part accounts for their popularity among the most 
careful laboratory workers. 
The whole story is told in our new 1913 Price Lists, which are gladly 
sent on application. 
We are sole agents for Spencer Microscopes for Great Britain and 
Ireland (except London). 
STANDLEY BELCHER & MASON, Ltd., Church Street, BIRMINGHAM 
Printed by Rican Cray & Sons, Limitrep, at Brunswick Street, Stamford Street, S.E., and published by MACMILLAN AND Co., Limtrep, at 
St. Martin’s Street, London, W, Cc. and THs MACMILLAN Co., 66 Fifth Avenue, New York.—Tuurspay, September 18, 1913. 
