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NATURE 
[FEBRUARY 26, 1914 
CONDENSER 
STATIC MACHINE 
System : Dr. Wommelsdorf. 
An important step in the 
evolution of Influence Machines. 
ENORMOUS OUTPUT. 
‘Suitable for Electro-culture. 
ISENTHAL & CO. 
Department 1), 
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Contractors to the Admiralty, War, India, and Colonial Offices, &c. 
SCIENTIFIC INSTRUMENTS 
OF ALL DESCRIPTIONS. 
The “HARRIS” 
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A cheap and reliable Instrument specially designed tor 
Students’ use. 
Very strongly constructed so that it may be used by 
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PRICE £2: 10:0 Each Net. 
Descriptive Pamphlet on application. 
PHILIP HARRIS & €0., iro. 
BIRMINGHAM 
(ENGLAND.) 
C. Winthrope Somerville’s 
- SULPHUR 
IN SPENT OXIDE — 
TEST. 
A reliable and rapid means of 
ascertaining the amount of sulphur 
in spent oxide. 
The result is given in percentage 
of sulphur direct. 
Complete instructions with each test. 
The set complete, £3 3 0 
SOLE MAKERS: 
TOWNSON & MERCE) 
34 CAMOMILE ST., LONDON, EC. 
Prof. HARTL’S| 
OPTICAL DISC 
POLARISING APPARATUS, 
; covering all the important 
pis: experiments in 
NATURE says :—“‘ Professoz Hartl 
has laid all teachers of experimental 
optics under an obligation by desi, 
a piece of apparatus which he calls 
‘optical disc’; this, at a moment's 
notice, can be adjusted so as to show 
the path of the rays in any one of thi 
important cases usually dealt with in 
elementary lectures on geometrica 
optics. The apparatus is very compact, 
and its general arrangement is so good 
. that one experiment may be changed 
pal Neo for another in about half a minute.” 
—_ a (See full notice in issue of 
. August 2, 1906+) 
SCHOOL WORLD says |—‘‘ Well worth the careful attention of thos 
interested in the teaching of optics. The whole apparatus should bey 
valuable for several reasons : ¢t) because each arrangement is very quickh 
produced ; (2) the effects are ¢trongly visible ; (3) measurements are readi 
made ; (4) the number of separate parts is small considering the varie 
of experiments which they render possible.” 
Send for Illustrated Descriptive Pamphlet 
post free from the SOLE AGENTS for the 
United Kingdom, India, and the Colonies, 
A. GALLENKAMP & CO., Ltd. 
19 & 21 SUN STREET, FINSBURY SQUARE, 
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