Your own sketches, 
photos, diagrams, 
etc. of mixed shapes 
and sizes converted 
into filmslides at 
the rate of 3d. per 
picture. Filmslide Lanterns—portable, simple, self-contained. Particularly 
useful for travelling lecturers and demonstrators. Price, £4 10 Oto £8. 
Particulars and Catalogue from 
VISUAL INFORMATION SERVICE 
The Original British Filmslide Producers 
168a BATTERSEA BRIDGE ROAD, LONDON, S.W.11 
FILMSLIDES 
A simplified system of lantern projection 
atch the thoughts you 
want to record before 
they fade away ! 
Speedwriting 
The NATURAL SHORTHAND 
is particularly well adapted to enable you 
to do this without conscious effort. 
A few hours interesting study, and you can 
write at the rate of one hundred words a 
minute with the letters you have always 
used. Learn a few simple rules in spare 
moments and begin using the system at 
once. Notes are always accurate and 
can be read with ease, even years after 
they have been made. 
Full particulars, post free, from :— 
SPEEDWRITING, LTD. 
51 Tothill Street, Westminster, 
LONDON, S.W.1. 
HEFFER’S BOOKSHOP 
for 
SCIENTIFIC BOOKS} PARWIN’S PARISH 
DOWNE, KENT 
We welcome correspond- es 
AC HIST ORY FOR 
ence on all matters con- 
cerning the buying and 
selling of Scientific Books 
and Periodicals, of which 
we hold a comprehensive 
stock 
Dr. O. J. R. HOWARTH 
Secretary of the British Association 
AND 
Mrs. HOWARTH 
With a Foreword by 
f Stir ARTHUR KEITH, F-.R.S. 
Catalogues ave issued at 
frequent intervals—are 
you on our mailing list ? 
RECENTLY ISSUED: 
CATALOGUE 450, 
SCIENTIFIC BOOKS 
AND PERIODICALS 
W. HEFFER & SONS, 
LTD., 
CAMBRIDGE, ENGLAND 
» 
+ 
° %, 
° 
° 
< 
- 
. 
Published by 
RussEL_ & Co., SOUTHERN COUNTIES, 
Lrp., SOUTHAMPTON 
To be obtained of all booksellers, or 
from Down House 
PRICE Is. 6d. 
POSTAGE 2d. 
