NATURE 



[September 21, 1905 



THE JUBILEE CATALOGUE 



ISSUED TO MARK THE 

 FIFTY YEARS' EXISTENCE OF THE FIRM 



OF 



E. LEYBOLD'S NACHFOLGER, 



eOLOGNE, 



Contains on its more than 900 pag-es a complete 

 survey of tlie apparatus used for instruction in 

 Physics, as well as numerous practical instruc- 

 tions and about 3000 illustrations. 



NATURE says: — "The firm of Leybold Nachfolger 

 in Cologne has recently issued a very complete and 

 interesting catalogue of physical apparatus and 

 fittings sold by them. The book starts with a history 

 of the instruments made in Cologne during the last 

 century. In its second section we find an account 

 of the construction and fittings of various chemical 

 and physical institutions. After this follows the cata- 

 logue proper, filling some 800 large pages, profusely 

 illustrated and admirably arranged. The book will be 

 most useful to the teacher." (No. 1846, Vol. 71.) 



THE CATALOGUE WILL BE FORWARDED TO SCHOOLS 

 AND INSTITUTES ON APPLICATION. 



LIQUID AIR AND LiQUID HYDROGEN. 



Dr. HAMPSON'S AIR-LIQUEFIER is now made to a standard pal- 

 tern, and numbers are in use in University Laboratories and elsewhere in 

 various countries. The whole apparatus is neat and compact and its parts 

 very easily moved ; the Liquefier, without stand, being a cylinder r? inches 

 high and 8 inches in diameter. 



It begins to liquefy air in from 6 to 10 minutes after the admission o"" air 

 at from 150 to 200 atmospheres pressure, making over a litre of liquid per 



It requires no auxiliary refrigerant and produces a perfectly cleat liquid 

 which requires no filtering u j 1 1 



The operator has only one jauge to watch and one valve to control. 



HYDROGEN LIQUEFIER to the designs of Dr. MORRIS V. . 

 TRAVERS for use in coniunction with Air-I.iouefier. 



For Prices and Particulars apply to the Sole Makers :— 



BRIN'S OXYGEN COMPANY, LIMITED, 



ELVERTON STREET, WESTMINSTER, S.W. 



'"zEISS FIELD-CLASSES 



WITH ENHANCED STEREOSCOPIC EFFECT. 

 x6, £6 O O. 



8, £6 10 O.J 



FOR TOURISTS. 



SPECIAL TYPES FOR NATURALISTS, 

 MARINE WORK, HUNTING, &c. 



Illustrated Catalogue, "Jn," Post Free on Application. 



CARL ZEISS. 

 JENA. 



Branches : 

 LONDON: 29 Margaret St., Regent Street, W. 



Berlin, Fr.inkfort o M, Hamburg, Vienna, St. Petersburg. 



DO YOU WISH 

 TO BE 



UP TO DATE 



BEWARE OF 



FEEBLE 

 IMITATIONa 



n Scientific Demonstrating ? 



full descriptive pamphle 

 the Kershaw. Patent Lantern 

 (Stroud and Rendall's and 

 Kershaw Patents), made of 

 best seasoned mahogany, 

 French polished, lined with 

 asbestos and Russian iron. 

 Fitted with two double 

 achromatic objectives, 90° 

 silvered prism, complete 

 with B.T. or mixed jet, in 



ALL ACCESSORIES SUPPLIED. ARC LAMPS, RESISTANCES, 

 STAHDS, &c. 



mII'^k a. KERSHAW, Dorring-ton St., Leeds. 



CONTR.iCrOR TO H..1I.'s GOrF.R.VM EXT. 



LAW OF 

 HELICAL SPRINGS 



The apparatus figured is substantially as described in Pro.. Perry's "Applied Mechanics," and 

 demonstrates the approximate truth of the following proposition : — If a given force be applied to 

 deform a given length of wire, the point of application of the force suffers the same linear displace- 

 ment, whether the wire is straight and the force applied to produce torsion in it from one end, or 

 whether the wire is coiled into a clo e helix and the force applied axially to produce extension from 

 one end ; provided that the arm of the effective moment in the first case is equal to the mean radius 

 of the helix in the second case. Price £4 O O 



IMMEDIATE DELIVERY. 



THE CAMBRIDGE SCIENTIFIC INSTRUMENT COMPANY, Lm 



caivibridge:, £:n^gil,an^i>. 



