Pee Wi K LY 
. To 
ILLUSTRATED JOURNAL OF SCIENCE. 
the solid ground 
Of Nature trusts the mind which builds 
for aye.” —Woxpswortu. 
No. 1421, VOL. 55] 
THURSDAY, JANUARY 
21, 1897. [PRICE SIXPENCE. 
Registered as a Newspaper at the General Post Office.] 
{All Rights are Reserved. 
NEWTONIAN X-RAY CURRENT METER. 
Gone principal difficulty in 
-Ray photography has 
Nea 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- 
posure then entirely depends, 
can be varied as desired and 
adjusted to the greatest 
nicety by the tension screw 
of the coil. 
““X” Rav Current Meter, comprising Ammeter and Volt- 
meter suitable for use with Induction Coils, £5 5s. 
SOLE Makers: 
NEWB TON & CO. 
5 Peis D REET, LONDON: 
List of Apps-Newton Induction Coils and X-Ray Apparatus Post Free 
on application. 
X-RAY COMPLETE SETS. 
IEWTON & 0 
LonpoN 
AuroRcs 
Ser A. Including 3-inch Coil, our own make, Batteries, Focus 
Tube, Tube Holder, Barium-Platino-Cyanide Screen, 
7in. X 5 in. £13 0 0 
SET Be. Tacleanie 6-inch Coil, Batteries, ‘Larger Focus Tube, 
Tube Holder, Barium- Platino- Cyanide Screen, 9f in. x 7in. £23 10 O 
{BARIUM-PLATINO-CYANIDE SCREENS. 
EXCELLENT FLUORESCEN CE, in neat ae with Handles. 
7 in. X 5 in,, 21s. 3 Of in. X 7 in., 32s. 6a. ; 11f in. X Ofin., 555. 
JOHN J. GRIFFIN & SONS, 
22 GARRICK STREET, LONDON, W.C. 
NALDER BROS. & GO., tonoon. 
D'ARSONVAL GALVANOMETER 
Delivered Free anywhere in U.S.A. for $32 C.0.D. 
Write for 
CATALOGUES. 
D'ARSONVAL 
CALVANOMETER 
(As illustrated). 
VERY PORTABLE. 
SENSITIVE. 
IN STOCK. 
£5 00 
NO AGENTS 
IN 
U.S.A. 
pBeRET & 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- 
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. 
Photographic Studios : Crystal Palace, 
