










































A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 
“* To the solid ground 
of Nature trusts the mind which buslds for aye. ”—WoRDSWORTH. 



No. 2792, VOL. 111] 
“SATURDAY, MAY 5 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, 
NEWTON'S 
EPISCOPE 
Moone: D 
ILLUSTRATIONS, 
NATURAL OBJECTS, 
etc. 
Price 
£31 10 0 
NEWTON & CO. 
ticians to 
the King. 
Estab. over 
200 years. 
Specialists in Optical Projection Apparatus, 
72 WIGMORE STREET, LONDON, wW.1. 




SCIENTIFIC INSTRUMENT MANUFACTURERS 
and LABORATORY FURNISHERS. 
DIRECT 
READING 
EXPANSION 
APPARATUS 
Price 
£2 2 0 
4 Descriptive Circular 
post free. 
PHYSICAL APPARATUS OF ALL KINDS 
FOR cOMecr> AND SCHOOLS. 

VITREOSIL 
LABORATORY WARE 
Superior to Porcelain 
Constant in Weight 
Best Substitute for 
Platinum 
and more Economical 
ASK YOUR DEALER FOR IT 
GIVE IT A 
TRIAL 

SOLE MANUFACTURERS 
THE THERMAL SYNDICATE, LTD., 
VITREOSIL WORKS—WALLSEND-ON-TYNE. 
LONDON DEPOT AE Tiber S.W.1. 

CTTTPTITUCVVNUVUHRUUNIUOOUODRRU DEOL LATO 
EGRETTI @ — 
38,HOLBORN VIADUCT.E.C.l. 
LONDON. 
Manufacturers of 
Meteorological Instruments 
to British and Foreign 
Governments. 

