A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. \%, 
“To the solid ground 
Of Nature trusts the mind which builds for aye.’’—WoORDSWORTH. 
@ 
Yonal Museu 
_No. 2218, Vor. 89] === THURSDAY, MAY 2, 1912 
_{Price SIXPENCE | 
__ Registered : asa a Newspaper + at the General Post Office.]_ 
The “INSTANTA” 
INDUCTION COIL 
The most Scientifically Designed 
and Efficient Coil in the World. 
le Makers: 
NEWTON & WRIGHT, L1p. 
(Late Electrical Department of Newton "e a 
72 WIGMORE STREET, LONDON, 
WRITE FOR ILLUSTRATED SL ae 
It is the Key to Success in Photography. 
Who can expect to excel who does not understand 
how to use the diaphragm, the swing back, the 
rising front, focussing scale, &c., &c.? All such 
questions are lucidly and simply explained in 
“PHOTOGRAPHIC LENSES : 
A SIMPLE TREATISE.” 
350 pages, 44 plates, numerous diagrams and 
illustrations, cloth bound. 
R. & J. BECK, Ltd., $8, SQR€5IL. | 
a ae 
8914. 
CYLINDROMETER, 
for measuring the curvature of lenses, 
provided with vernier. It consists of 
a plain rectangular metal plate, with 
a rectangular recess of accurately 
known dimensions cut out of it. It 
is applied to the surface of a cylinder 
or sphere as shown in the illustration, 
the distance C D is measured directly 
by means of small steel scale, with 
vernier reading, and the distance A B 
and C E being known, the radius of 
the cylinder or sphere can at once be 
calculated from the lengths of A B 
and DE by the usual application of 
Euclid III. Stock size. Dimensions 
of recess, 5 cm. by 5 cm. 
£0 15.6 
(EXTRACT FROM NEW 
PHYSICAL LIST.) 
(all “Rights Reserved. 
Loan 
ar 
| 
BAIRD & TATLOCK (London), LTD., 
Negretti & Zambra’s 
new patent 
14 Cross Street, Hatton Garden, London, E.C. 
WIND DIRECTION RECORDER 
proves a simple solution to an awkward problem. 
Descriptive pamphlet sent post free. 
38 Holborn Viaduct, London, E.C. 
Branches 
45 JN 
Cornhill, 
pes 
