COX'S NEW PORTABLE

HIGH FREQUENCY APPARATUS

GIVING GENUINE H.F. CURRENTS
which may be exactly regulated.

FOR SALE.

30 moving coil ammeters and voltmeters.

6 moving coil reflecting and pointer galvanometers.

8 hot wire ammeters and voltmeters.

50 electromagnetic ammeters and voltmeters.

60 dynamos and motors, direct and alternating current.

40 ironclad regulating rheostats.

20 transformers and choking coils.
10 induction coils, 10-inch spark.
3 mercury jet breaks.

Standard condensers, Wheatstone bridges, static machines, switches, cables, &c., by various makers, at low prices.

G. BOWRON, 57 EDGWARE RD., LONDON, W.

ALFRED E. DEAN,

THE LARGEST MAKER IN ENGLAND of Apparatus in all Departments of

ELECTRO-THERAPEUTICS

including Radiography, High Frequency, Hydro-Electric and
Light Baths, Finsen and other Light, Cautery, Electrolysis, &c.
INDUCTION COILS AND STATIC MACHINES A SPECIALITY.
CONTRACTOR TO THE WAR OFFICE, INDIA OFFICE, AND ADMIRALTY,
BRITISH AND FOREIGN HOSPITALS, &C.
LISTS ON APPLICATION.

82 HATTON GARDEN, LONDON. For Sale.-Extensive Collections of British Lepidoptera, Coleoptera, Tropical Butterflies, Cabinets, &c. Correctly named type collections at very moderate prices.-Particulars from A. FORD, Hillside, Sunnyhill, Pokesdown, Bournemouth.

THIRD ENGLISH EDITION.

THE PRINCIPLES OF

CHEMISTRY.

By D. MENDELÉEFF.

Translated from the Russian (Seventh Edition) by
GEORGE KAMENSKY, A.R.S.M.,

Of the Imperial Mint, St. Petersburg,
And Edited by

THOMAS H. POPE, B.Sc., F.I.C.
With 110 Diagrams and Illustrations. 2 vols.
8vo. 32s. net.
Prospectus Sent on Application.
LONGMANS, GREEN, & CO., 39 Paternoster Row, London, E.C.
JUST PUBLISHED, with 21 Illustrations and a Coloured
Map. Crown 8vo.
95. net.

AN INTRODUCTION TO THE
GEOLOGY OF CAPE COLONY.

By A. W. ROGERS, M.A., F.G.S.,
Director of the Geological Survey of Cape Colony.

With a Chapter on the Fossil Reptiles of the Karroo Formation by
R. BROOM, M.D., B.Sc., C.M.Z.S.

This work contains a Chapter which deals scientifically with the subject of Volcanic Pipes. These pipes are filled with the famous diamond. iferous Blue Ground which forms the raw material of the vast diamondmining industry of South Africa.

LONGMANS, GREEN, & CO., 39 Paternoster Row, London, E.C.

JUST PUBLISHED. Crown 8vo. 3s. 6d. net.

"N" RAYS.

Sciences. With additional Notes and Instructions for the

Construction of Phosphorescent Screens.

By R. BLONDLOT,

Correspondent of the Institute of France, Professor in the University

of Nancy.

and Dealers in Scientific, Literary, and other Journals and Reviews, and Publications of Learned and Scientific Societies, in Complete Sets, Volumes, or Parts.

Agents for British, Foreign, and Colonial Libraries, Institutions, and Private Book Buyers. Current Catalogue sent post free on application. Books sought for. Correspondence Invited. All communications answered. LIBRARIES OR SMALL COLLECTIONS OF BOOKS PURCHASED. All Orders promptly executed. Established 1820.

BARGAINS FOR BOOKBUYERS. POST FREE. A February SUPPLEMENTARY CATALOGUE of Publishers' Remainders and other acquisitions at greatly reduced prices, comprising works in the VARIOUS BRANCHES of SCIENCE; Medicine; Travel, Sport and Adventure; Biography; Fiction; &c.

NEW BOOKS SENT BY POST TO ALL PARTS AT DISCOUNT PRICES (except those published net) plus postage.

H. J. GLAISHER, Remainder & Discount Bookseller,

57 Wigmore Street, London, W.

THOMAS PRINCE,

SCIENTIFIC BOOKSELLER.

All books advertised and reviewed in NATURE are supplied

at lowest cash prices.

Orders by post promptly dispatched. 85 PRAED STREET, LONDON, W.

At the

W. H. DAVISON, M. A., Clerk to the Governing Body.

POLYTECHNIC,

SOUTH-WESTERN Manresa Road, Chelsea, S.W., Day College Courses of thirty hours per week will be conducted in preparation for the London University Degrees of B.Sc. in Mechanical and Electrical Engineering, in Chemistry, Physics and the Natural Sciences. The composition fee for the Session of three terms, 1904-1905, is £15. These Courses are recog nised for "Internal Students of the University, and consist of lecture and laboratory instruction. The Courses are conducted by :MECHANICAL ENGINEERING, W. W. F. Pullen; ELECTRICAL ENGINEERING, A. J. Makower; CHEMISTRY, J. B. Coleman, J. C. Crocker, and F. H. Lowe; MATHEMATICS and PHYSICS, S. Skinner, W. H. Eccles, J. Lister and L. Lownds; BOTANY, H. B. Lacey and T. G. Hill; GEOLOGY, A. J. Maslen. In the evenings similar Courses will be conducted, but at £2 per Session. Also TECHNICAL DAY COURSES of three years' duration are arranged as a preparation for the Engineering, Electrical and Chemical and Metallurgical professions. The Laboratories and Workshop are open for RESEARCH under the direction of the Principal and the Heads of Departments.

Further particulars may be obtained on application to the SECRETARY, who will send either the Day College Prospectus and Calendar or the Evening Class Prospectus for 3d. The Prospectuses may be had at the Office for id.

ROYAL INSTITUTION OF

GREAT BRITAIN.

ALBEMARLE STREET, PICCADILLY, W. SATURDAY next, February 25, at Three o'clock, DAVID GEORGE HOGARTH, Esq., M.A. First of two Lectures on "Archæology." Half-aGuinea the Course.

TUESDAY, February 28, at Five o'clock, Professor KARL PEArson, F.R.S. First of three Lectures on "Some Recent Biometric Studies." Half-a-Guinea,

THURSDAY, March 2, at Five o'clock, Professor H. H. TURNER, D.Sc., F.R.S. First of three Lectures on "Recent Astronomical Progress. Half-a-Guinea,

Subscription to all Courses in the Season, Two Guineas.

BRITISH MUSEUM.

The READING ROOMS will be CLOSED from WEDNESDAY, MARCH 1, to SATURDAY, MARCH 4, inclusive.

(4) GEOLOGY. Salary, £350 per annum.

(3) ZOOLOGY. Salary, £350 per annum.

The professors of Geology and Zoology will also hold appointments in connection with the Albany Museum, for which they will receive an additional salary of £150 each per annum.

Further particulars may be obtained from the AGENT-GENERAL FOR THE CAPE OF GOOD HOPE, 100 Victoria Street, Westminster, London, to whom applications, with copies of testimonials, should be sent on or before March 15, 1905.

Applicants must be under 40 years of age, and must furnish a certificate of good health.

Successful candidates will be required to enter upon their duties at Grahamstown on July 25, 1905.

THE LISTER INSTITUTE OF
PREVENTIVE MEDICINE.

JENNER MEMORIAL STUDENTSHIP IN BACTERIOLOGY. The Governing Body offers Research Studentship of the value of £150, tenable by a British subject for one year, but renewable for a second year at the option of the Governing Body.

Applications to be sent in by March 18, 1905, to the ASSISTANT SECRETARY.

The Lister Institute of Preventive Medicine,

Chelsea Gardens, Chelsea Bridge Road, London, S. W.

COUNTY BOROUGH OF HUDDERS

FIELD.

TECHNICAL COLLEGE.

Principal-J. F. HUDSON, M.A., B.Sc. ASSISTANT LECTURER and DEMONSTRÁTOR in CHEMISTRY required. Some teaching experience necessary. Salary, £110. Statement of duties on application to THOS. THORP, Secretary.

TO SCIENCE AND MATHEMATICAL MASTERS.-Easter (1905) Vacancies.-Graduates and other well qualified Masters seeking posts in Public and other Schools for next term should apply at once, giving full details as to qualifications, &c., to Messrs. GRIFFITHS, SMITH, POWELL & SMITH, Tutorial Agents (Estd. 1833), 34 Bedford Street, Strand, London. Immediate notice of all the best vacancies will be sent.

REQUIRED as soon as possible, TWO SCIENCE MASTERS. (1) Chemistry, Botany, and some Physics. Salary, £150 to £160. Technical School. (2) Chemistry, Mathematics, and Botany. £140. County School. For particulars address GRIFFITHS, SMITH, POWELL & SMITH, Tutorial Agents (Estd. 1833), 34 Bedford Street, Strand, London.