xliv 
NATURE 
[SEPTEMBER 25, 1913 
Simmance & Abady’s 
MICROMETER 
PRESSURE & VACUUM 
GAUGE 
indicates in thousandths of an inch, 
where other gauges only show tenths. 
Indispensable for accurate 
experiments. 
Made in suitable ranges to requirements. 
SOLE MAKERS :— 
ALEXANDER WRIGHT & CO. 
LTD. 
WESTMINSTER. 
SCIENTIFIC INSTRUMENTS 
OF ALL DESCRIPTIONS. 
The *“ HARRIS ” 
SPECTROMETER. 
4 
A cheap and reliable Instrument specially designed for 
Students’ use. 
Very strongly constructed so that it may be used by 
elementary pupils without being put out of order. 
PRICE £2: 10:0 Each Net. 
Descriptive Pamphlet on application. 
PHILIP HARRIS & CO., 
BIRMINGHAM 
(ENGLAND.) 
(1913) 
LTD. 
M'TOWNSON & MERCER] 
LTD. 
(Established 1798), 
Manufacturers of Apparatus tor 
CHEMISTRY, PHYSICS, MECHANICS, 
BACTERIOLOGY, METALLURGY, 
and. all Science Subjects. 
LABORATORIES FURNISHED AND COMPLETELY EQUIPPED. 
Apparatus for Students’ Use. 
Sole Agents in the United Kingdom for 
Becker’s Sons’, Rotterdam, Balances and Weights. 
Agents for the Glassware of Josef Kavalier and Schott & Gen. 
and Sehleicher & Schiill’s Filter Papers. 
Contractors to the Home and Colonial Departments of H.M. Government, 
War Office, India Office, Imperial College of Science and Technology and 
the Universities and Principal Technical Institutions, County Councils, &c. 
34 Camomile Street, London, E.C. 
Students’ Spectroscope 
With 28 mm. dense flint prism on rotating base, prism 
easily removable, circle divided 360° with vernier 
reading to 5 minutes, adjustable slit with comparison 
prism, sliding adjustment allowing of movement in all 
directions to suit position of light. Collimator and 
Telescope can be clamped in any position round the 
divided circle. The whole can be raised or lowered 
by means of sliding rod, fixed to extra heavy tripod 
foot, weighing 4lbs., which is also £3 10 0 
furnished with levelling screws 
Extract from List of Spectroscopes (No. 54), 
a copy of which will be sent on application. 
A. GALLENKAMP & Co., Ltd., 
19-21 Sun St., Finsbury Square, London, E.C. 
“Printed by RicHarp Cay & Sons, Limirep, at Brunswick Street, Stamford Street, S.E., and published by MAcMILLAN anv Co,, LimireEp, at 
St. Martin's Street, London, W.C., and THe Macmitvan Co., 66 Fifth Avenue, New York.—TuHurspay, September 25, 1913. 
