


















































A WEEKLY ILLUSTRATED JOURNAL OF SCTIEN€F: 
Tonal. meat 
“* To the solid ground 
Of Nature trusts the mind which builds for aye. ”—WoRDSWORTH. 


No. 2786, VOL. 111] 
SATURDAY, MARCH 24, 1923 
[PRICE ONE SHILLING 



[All Rights Reserved. 


Registered as a Newspaper at the General Post Office.] 
i: ppeda S EPISCOPES 
for the projection of 
OPAQUE OBJECTS 
including 
MAPS, DRAWINGS, 
DIAGRAMS, PRINTED 
and TYPED MATTER, 
ILLUSTRATIONS, 
NATURAL OBJECTS, 
etc. 
Price list on application. 
(MODEL Cc.) 
Estab. over 
HE the King, N EWTON & CO. 200 years. 
Specialists in Optical Projection Apparatus for Visual Instruction, 
72 WIGMORE STREET, LONDON, wW.1. 











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


REYNOLDS & BRANSON, Ltd. 
Chemical and Scientific Instrument Makers to His Majesty’s 
Government (Home and Overseas Dominions). 
LABORATORY FURNISHERS and MANUFACTURING CHEMISTS. 
WORKS AND OTHER 
LABORATORIES 
equipped 
with Benches, Fume 
, Chambers, Apparatus, 
Balances, 
Chemicals, etc. 
Designs and quotations 
submitted on application 
BRITISH-MADE Glass, Porcelain, 
Nickel Ware, and Filter Papers. 
Apparatus in Glass, Metal, or Wood made 
to customers’ own Designs. 
CATALOGUES POST FREE. 
Enquiries for Technical Chemicals in quantity solicited. 
14 COMMERCIAL STREET, LEEDS. 
HUMIDITY 



RECORDING ASSMAN 
PSYCHROMETER 
with Ventilating Fan and Electric Motor. 
Write for full particulars. 
EGRETTI @ ZAMBRA 
38, HOLBORN VIADUCT.E.C.1. 
LONDON. 
