A WEEKLY 
ILLUSTRATED JOURNAL OF SCIENCE. 
“©To the solid ground 
Of Nature trusts the mind which builds for aye.” —WORDSWORTH. 
No. 1420, VOL. 55] 
THURSDAY, JANUARY 14, 1897. 
[PRICE SIXPENCE. 
Registered as a Newspaper at the General Post Office.] 
{All Rights are Reserved. 
NEWTONIAN X-RAY CURRENT METER. 
oa principal difficulty in 
- Ray photography has 
aA to judge the length of 
exposure. This can easily be 
done “by using an X-Ray 
Current Meter. The arrange- 
ment answers the purpose 
admirably. The same con- 
ditions can, if desired, be re- 
produced from day to day, 
and the voltage being con- 
stant, the number of amperes, 
on which the rapidity of ex- 
can be varied as desired and 
adjusted to the greatest 
of the coil. 
*““X%” Ray Current Meter, comprising Ammeter and Volt- 
meter suitable for use with Induction Coils, £5 5s. 
So_e Makers: 
NEWTON & CO. 
3 FLEET STREET, LONDON. 
List of Apps-Newton Induction Coils and X-Ray Apparatus Post Free 
on application. 
BECK'S MICROSCOPES. 
No. 25a. —THIS MODEL, with 
I-in. and }-in. Object Glasses, 
Two Eyepieces, and packed 
in Polished Mahogany Case, 
£6 10s. 
. 258. THIS MODEL, with 
3-in. and }-in. Object Glasses, 
Two Eyepieces, and packed 
in Polished Mahogany Case, 
£7 5s. 
29B.—The addition of Abbe 
Condenser to 25B with Iris 
Diaphragm and Focussing 
and Swinging Adjustments, 
£8 15s. 
FULL PARTICULARS FREE on APPLICATION to 
R. & J, BECK, LT0., 68 CORNHILL, LONDON, E.¢. 
No. 
STAND No. 25. 
posure then entirely depends, | 
nicety by the tension screw | 
RIPPON 
ASTRONOMICAL. TELESCOPE. 
With 3-inch Achromatic Object-Glass of excellent quality, with brass body, 
one ‘Terrestrial and two Celestial Eyepieces, in Case complete... Guaranteed 
to be capable of dividing Double Stars and showing Saturn's ‘Ring and 
Jupiter's Belts, 
Price £6 10s. Od. 
Catalogue of Astronomical Telescopes sent Free. - 
JOHN BROWNING, 63 STRAND, LONDON, W.C. 
“NBGRETT! & ZAMBRA’S THERMOMETERS. 
The outside Window Bracket Thermometer 
enables the observer to read the Present 
Temperature from inside the House. 
PRICE 21/- and upwards, 
Accurate Thermometers for all Purposes. 
ILLUSTRATED PRICE LISTS FREE TO ALL PARTS OF THE WORLD. 
NEGRETTI. & ZAMBRA, 
Scientific Instrument Makers to Her Majesty the 
Queen and British and Foreign Governments, 
38 HOLBORN VIADUCT. 
BRANCHES— 
45 Cornhill, and 122 Regent Street, London. 
Crystal Palace. 
Photographic Studios : 
