September 21, 1905 J 



NATURE 



Physical 



and 



Chemical 



Laboratories 



completely 



fitted up. 



HEELE'S FAMOUS SPECTROMETER. Price £10 10 O 



Including dense flint glass prism, with micrometer movement, reading to i minute. Universally acknowledged to be the 



most efficient instrument on the market. 

 Also, smaller size, Price £6 nett, including two prisms, one being a hollow prism. As supplied to the Royal College of Science, 

 Dublin, University College, Gower St., London County Council, St. Munchin's College, Limerick, and many other leading Institutes. 



DELIVERY FROM STOCK. 



I>ETER HEELE, XX5 Hi^h HColborn, \Sl.C, 



MAKER OF PHYSICAL, ASTRONOMICAL, AND OTHER INSTRUMENTS. 



IMPORTANT REDUCTION l.\ I'RICF. 



SPINTHARISCOPE. 



SIR WILLIAM CROOKES. 



Showing thR Scintillations of Radium. 



Price witll powerful Lens, and contained in 

 neat Leather case, 15/- Post free anywhere. 



The scintillations seen in this instrument are 

 from Pure Radium Bromide of the highest 

 known activity, and are brighter and more 

 plentiful than those produced from Pitch 

 blende or other bodies of low Radio Activity. 



I*- See letter from Proi'. Gotch on " The 

 Spinthariscope and Retinal Excitability" 

 (Nature, June 22, 1905, page 174), setting 

 forth a valuable scientific application of the 



A.. C. COSSOR, 



54 FARRINGDON ROAD, LONDON, E.C. 



Telephone, toq47 Central. 

 Gold Medal St. Louis Kxhihition, tgo4. 



RARE 



CHEMICALS 



METALS 



MINERALS 



For LabOFatory, Scientific, and all other 

 purposes. 



RADIUM SALTS & RADIO-ACTIVE PREPARATIONS. 

 CALCIUM METAL, 1/6 oz.; 20/- lb. 



Price List on Application. 



HARRINGTOIST BROS., 



ChfiiiUal JUaiiiifrntiii-eis niid Dealers, 



4 OLIVER'S YARD, CITY ROAD, LONDON, E.C. 



HOPKIN & WILLIAMS, Ltd. 



16 GROSS STREET, HATTON GARDEN, LONDON, E.C. 



Works-ILFORD. E. 



PURS CiHEIVEICAlLiS 



For TEACHING, RESEARCH, and TECHNOLOGY. 



NEW 

 SURFACE 



DOUBLE 

 CONDENSER. 



THE "IDEAL." 



This is the best and 



apest Conde 



by oute 

 (f^^ flow into th 



all delicate parts 

 :et. and the water cannot 

 distillate. Made in two si; 

 and 8", 4/6 and 5/6 each. 



^1^" Nature says: — " 

 pact and efficient condense 

 notice. We have tested it 

 substances as ether, carbi 

 and have found that ever 

 condensation is very com 

 in order to condense these 

 is necessary to employ a ve 

 this means using a great 



the 





lis is one of the most com- 

 which has come before our 

 r condensing such volatile 

 disulphide, and acetone, 

 'ith rapid distillation the 

 te. Generally speaking, 

 ibstances satisfactorily, it 

 long condenser ; of course, 

 of bench space. As 



I a perpendicular posi- 



ery great." 



SOLE Jl/AA'ERS— 



BREWSTER, SMITH & CO., 



6 CROSS STREET, 



FINSBURY P AVEMENT, LONDON, E.C 



All kinds of Apparatus for Science Teaching. 



