














A WEEKLY ILLUSTRATED JOUR 
NAL OF SCIENCE, 
“* To the solid ground 
Of Nature trusts the mind which builds for a aye. ”—WoRDSWORTH. 


No. 2782, VoL. 111] 
SATURDAY, FEBRU ARY 24, 1923, 


_[PRICE ONE SHILLING 





Registered as a Newspaper at the General Post Office. ] 
[All Rights Reserved. 


NEWTON’S 
Model D 
EPISCOPE 
for the projection of 
OPAQUE OBJECTS 
including 
MAPS, DRAWINGS, 
DIAGRAMS, PRINTED 
and TYPED MATTER, 
ILLUSTRATIONS, 
NATURAL OBJECTS, 
etc, 
NEWTON'S 
EPISCOPE 
Move: D 
Price 
£31 10 0 
ticians to NEWTON & CO. Estab. over 
the King. 200 years. 
Specialists in Optical Projection Apparatus, 
72 WIGMORE STREET, LONDON, wW.1. 

14-15 CROSS STREET, 
HATTON GARDEN, E.C.1. 
SIMPLE 
MICROBAROGRAPH 
Showing fall in barometric 
pressure by so small a rise 
as one foot. 
Pamphlet giving working 
instructions and 
ments sent with instrument. 
experi- 
PRICE 
£1 12 6 



REYNOLDS & BRANSON, Lto. 
Chemical and Physical Apparatus Makers to hie? Majesty's 
Government (Home and Overseas Dominions), 
Laboratory Outfitters, &c. 
Gold Medals at Allahabad and London. Grand Prix and Gold Medal 
at the Enternational Exhibition, Turin. 
APPARATUS for MACKENZIE 
and FORSTER’S THEORETICAL 
and PRACTICAL MECHANICS and 
PHYSICS as adopted by H.M. 
Government and many important 
Educational Authorities, Price Lists 
on application. 




VivE :—‘‘ Theoretical and 
Practical Mechanics and Phy- 
a sics,” by A. H. MACKENZIE, 
M.A., B.Sc., and A. ForsTEr, 
B.Sc. 
Wireless Apparatus and Accessories supplied. 
CATALOGUES POST FREE. 
Optical Lanterns and Lantern Slides; Chemical and Physical Apparatus 
and Chemicals of Guaranteed Purity, including ‘‘A.R.” Quality 
(New Edition). 
14 COMMERCIAL STREET, LEEDS. 

HUMIDITY 
en. = 



RECORDING ASSMAN 
PSYCHROMETER 
with Ventilating Fan and Electric Motor. 
Write for full particulars. 
EGRETTI @ ZAMBRA 
38, HOLBORN VIADUCT. E.C11. 
LONDON. 
