A WEEKLY 
ILLUSTRATED JOURNAL OF SCIENCE. 
“To the solid & 
Of Nature trusts the mind which butids for aye. 
yound 
”__WORDSWORTH, 
No. 1422, VOL. 55] 
THURSDAY, JANUARY 28 
7 lSOz7s [PRICE SIXPENCE. 
Registered as a Newspaper at the General Post Office.] 
ah [All Rights are Reserved. 
NEWTONIAN X-RAY CURRENT METER. | 
ee principal difficulty in 
-Ray photography has 
ans 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- 
IEWTON & C2 
Lonoon 
“erent on which the rapidity of ex- 
posure then entirely depends, 
can be yaried as desired and 
adjusted to the greatest 
nicety by the tension screw 
of the coil. 
stant, the number ofamperes, | 
| 
RIPPON = _— 
ASTRONOMICAL TELESCOPE, 
““X* Ray Current Meter, comprising Ammeter and Volt- | With 3-inch Achromatic Object-Glass of excellent quality, with brass body, 
meter suitable for use with Induction Coils, £5 5s. 
SoLreE Makers: 
NEW$BTFON & CO. 
3 FLEET STREET, LONDON. 
List of Apps-Newton Induction Coils and X-Ray Apparatus Post Free 
on application. 
Warr. 
mea BECK Ae. pon Dow AY, 
Y i if 
should 
de without a 
free 
on application. 
R.& J. BECK, Ltd., 68 Cornhill, London, E.C. 
one Terrestrial and two Celestial Eyepieces, in Case complete. Guaranteed 
| to be capable of dividing Double Stars and showing Saturn's Ring 
| Jupiter's Belts, 
and 
Price £6 10s. Od. 
Catalogue of Astronomical Telescopes sent Free. 
JOHN BROWNING, 63 STRAND, LONDON, W.C. 
No Scientific Man | ‘NEGRETT & 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 al/ Purposes. 
ILLUSTRATED PRICE LISTS FREE TO ALL PARTS OF THE WORLD- 
Full particulars | 
| 
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NEGRETTI & ZAMBRA, 
Scientific Instrument Makers to Her Majesty the 
Queen and British and Foreign Governments, 
38 HOLBORN VIADUCT. 
BRANCHES— 
Hf 
ll 
45 Cornhill, and 122 Regent Street, London. 
Photographic Studios : Crystal Palace. 
