rs Os eae 
Anon at 
5 Ae are ee pia , : = = fa ie 
A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. . ; 
“To the solid ground NW 
Of Nature trusts the mind which builds for aye. ’—WorpswortH. Sitiong os] Mus 
No 2214, V VoL. 80] THURSDAY, APRIL 4, 1912 [PRICE SIXPENCE 
_ Registered [as a Newsp aper at the General | Post Office. ] : ok Trae a [all Rights, Reserved. 
8914. 
NEWTON & Cos 
NEW MODEL 
ASTRONOMICAL 
TELESCOPE. 
Complete with 34 in. object 
glass, 2 eyepieces, finder, Xc. 
on altazimuth stand. 
Complete, 
£15 
By Royal Warrant to H.M. the King. 
72 WIGMORE STREET, LONDON, 
Established over 200 Years Telegrams: 
1/- 
By Post 
1/3 
Ww. 
“ Newtobar, London.” 
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, numerous diagrams and 
cloth bound. 
R. & J. BECK, Ltd., 8, CORNHILL, 
7 London, E.c. 
44 plates, 
illustrations, 
STUDY 
rue LENS 
| the cylinder or sphere can at once be 
calculated from the lengths of A B 
CYLINDROMETER, 
for measuring the curvature of lenses, 
provided with vernier. It consists of 
a plain rectangular metal plate, wh 
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 
and D E 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.) 
BAIRD & TATLOCK (London), LTD., 
14 Cross Street, Hatton Garden, London, E.C. 
© 2G 0 GE > es 6 EE $e 
N. & Z.’s latest instrument is a 
Wind Direction Recorder 
that accurately registers with 
a single pen ona rectilinear 
chart every change in the 
direction of the wind. 
Complete with vane, 20 feet 
of spindle, 400 charts, &c., 
Bie. £17): /10) = 0 
1S 
Descriptive Pamphlet, and List 
Meteorological Instruments, post free. 
Negretti & Jame 
Holborn Circus, London, 
45 Cornhill, E.C.; 122 ame or W. 
tS 6 eS ¢ FS ee 
of 
| 
e e 
| 
¢ ¢ 
| | 
e ¢ 
e 4 
| 
S ¢ 
