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A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE

To the solid ground
01 Nature trusts the mind which builds for aye." —WORDSWORTH.

No. 1850, VOL. 71]
THURSDAY, APRIL 13, 1905

[PRICE 15 CENTS Registered as a Newspaper at the General Post Office.]

[All Rights are Reserved. The “NEWTONIAN”

REYNOLDS & BRANSON, Ltd.
Chemical and Scientific Instrument Makers to His Majesty's

Government (Indian, Home, and Colonial).
LABORATORY FURNISHERS and MANUFACTURING CHEMISTS.

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Can be worked from any House Supply. Complete with
Spirit Lamp, 9 feet of Double Cable, and all Connections.
With Single Filament

25s.
With Triple Filament

50s. On a 200-Volt Circuit the Triple gives 1000 Candle-power

nominal.

CHEMICAL AND PHYSICAL BENCH, illustrated above, as supplied to National Physical Laboratory, Teddington, fitted for Gas, Water

and Electricity.
Catalogue of Chemical and Physical Apparatus, 350 op. and 1200

Illustrations, free on application.
DESIGNS OF BENCHES AND FITTINGS TO SUIT ALI. REQUIREMENTS.

14 COMMERCIAL STREET, LEEDS.

NEWTON & CO., 3 FLEET STREET, LONDON.

THE NEW BOOK

NEGRETTI & ZAMBRA'S

SELF-RECORDING METEOROLOGICAL INSTRUMENTS.

PRICE ONE SHILLING.

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Containing an original description of the principles and function of the photographic lens. Together with the

latest workshop methods. Then there follows a series of chapters on practical photography and the effect of lenses on results. The chief types are discussed and compared by means of original diagrams. Also an appendix on the Gauss Theory and on a new system of lens testing. The book

is entitled
“PHOTOGRAPHIC LENSES:

A SIMPLE TREATISE."
By CONRAD BECK and HERBERT ANDREWS.

POST FREE 1/3
350 Pages, 45 Engravings, 150 Diagrams, Cloth Bound.

EDITION DE LUXE, 3/6 POST FREE,
R. & J. BECK, Ltd., 68 CORNHILL, LONDON.

THE NEW PATTERN COMBINED BARO-THERMOGRAPH. The above instrument combines in one apparatus the Recording Baro. meter and Recording Thermometer, giving thus on one and the same chart continuous records of the atmospheric pressure and temperature for seven days. Illustrated Price Lists of Self-Recording and other Scientific

Instruments Post Free to all parts of the World.

38 HOLBORN VIADUCT, E.C. Branches-45 CORNIIILL, and 122 REGENT STREET.

OPTICAL CONVENTION, 1905.

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BIRKBECK COLLEGE,

BREAMS BUILDINGS, CHANEERY LANE, E.C.
President :

FACULTY OF SCIENCE.
Dr. R. T. GLAZEBROOK, M.A., F.R.S.,

DAY AND EVENING COURSES.
Director of the National Physical Laboratory.

Chemistry
Vice-Presidents:

SJ. E. MACKENZIE, Ph.D., D.Sc

(H. WREN, Ph.D., BA., B.Sc. Sir WM. De Wiveleslie ABNEY, K.C.B., D.C.L, F.R.S.

(ALBERT GRIFFITHS, D.Sc. The Right Hon. The LORD BLYTHSWOOD.

Physics ...

D. OWEN, B.A., B.Sc.
Sir W. H. M. CHRISTIE, K.C.B., M.A., F.R.S.,

(B. W. CLACK, B.Sc.
Astronomer Royal. Mathematics

E. H. SMART, M.A.

*** (W. G. Birt, B.A., B.Sc. The Right Hon. THE EARL OF CRAWFORD, K.T., LL.D., F.R.S.

Botany

SA. B. RENDLE, M.A., D.Sc. MR. Thos. R. Dall'EYER, F.R.A.S.

F. E. FRITSCH, Ph.D., B.Sc The Hon. ALBAN G. H. Gees, M.A., M.P.,

Zoology ...

H. W. UNTHANK, B.A., B.Sc.
Master of the Worshipful Co. of Spectacle Makers. Geology & Mineralogy Geo. F. HARRIS, F.G.S.
Sir Howard GRUBB, F.R.S.

Assaying, Metallurgy & Mining. Geo. PATCHIN, A.R.S.M The Right Hon. THE LORD KELVIN, O.M., G.C.V.O., F.R.S. RESEARCH in Chemistry and Physics in well-equipped laboratories. The Right Hon. The LORD RAYLEIGH, O.M., D.C.L., F.R.S. French, German, Spanish, Russian, Dutch, & Italian Classes. The Right Hon. The Earl Of Rosse, K.P., D.C.L., F.R.S.

EVENING CLASSES also in Biology, Physiology, Practical Geoder HE OPTICAL CONVENTION will be held at the North.

Building and Machine Construction, Steam, Theoretical and Apple AMPTON INSTITUTE, CLERKENWELL, E.C., from May 31 to

Mechanics, Land and Quantity Surveying, and Estimating. June 3, inclusive.

Calendar 6d. (post free 8d.), on application to the SECRETARY. The object of the Convention is to bring into co-operation those interested in Optical Matters, from all sides of the question, theo. retical, practical, and commercial.

ST. THOMAS'S HOSPITAL, The mornings will be devoted to papers and discussions on Optical subjects. These will be collected in a volume to be issued by the

ALBERT EMBANKMENT, S.E.
Convention.
There will be an

(UNIVERSITY OF LONDON.) EXHIBITION OF OPTICAL & SCIENTIFIC INSTRUMENTS

The SUMMER SESSION will COMMENCE on APRIL 26. of British manufacture, in the large hall of the Northampton Institute,

The Hospital occupies one of the finest sites in London, and contains bea during the Convention, open daily from 12 to 10 p.m. In connection

Beds, of which 540 are in constant use. with this, a catalogue is in preparation, which will be a useful work

Entrance and other Scholarships and Prizes (26 in number) of the vale. of reference in regard to instruments manufactured in this country.

of more than £500, are offered for competition each year. The Subscription for Membership of the Convention will be five Upwards of 60 Resident and other Appointments are open to Student shillings. Applications for membersbip should be addressed to the after qualification. Hon. Sec., Mr. F. J. SELBY, M.A., Elm Lodge, Teddington,

A Students' Club forms part of the Medical School Buildings, and the Middlesex, who will be glad to furnish further particulars if desired.

Athletic Ground, nine acres in extent, situated at Chiswick, can be reacted

in forty minutes from the Hospital. ADMISSION to the Exhibition, daily, ONE SHILLING,

A Prospectus, containing full particulars, may be obtained from the after 7 p.m., Sixpence.

undersigned. Tickets admitting to the Exhibition at any time while it is open, 2/6.

J. H. FISHER, B.S. Lond., Dean.

THE

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(UNDER THE AUSPICES of His MAJESTY'S GOVERNMENT, I UNIVERSITY OF BIRMINGHAM. THE LONDON SCHOOL OF TROPICAL faculties.

MEDICINE.
SOIENOE, ARTS, MEDIOINE, COMMERCE.

(UNIVERSITY OF LONDON.)
SPECIAL SCHOOL OF MODERN LANGUAGES.
DEPARTMENT FOR TRAINING OF TEACHERS.

CONNAUGHT ROAD, ALBERT DOCK, E.
Scbools ot-

(IN CONNECTION WITH THE HOSPITALS OF THE SEAMEN | ENGINEERING, METALLURGY, MINING, BREWING,

HOSPITAL SOCIETY.)
DENTISTRY,

The next SESSION commences on MONDAY, MAY 1, 1905.
Leading to Degrees and Diplomas.

For Prospectus, Syllabus, and other particulars, apply to tbe Secretary

P. MICHELLI, Esq., Seamen's Hospital, Greenwich, S.E.
All Courses AND DEGREES ARE OPEN TO BOTH MEN AND WOMEN
STUDENTS.
In the Medical School there is a separate Dissecting Room for Women

THE LONDON SCHOOL OF TROPICAL with a qualified Woman Demonstrator.

MEDICINE. Graduates of other Universities may, after two years' study or research, take a Master's Degree.

“CRAGGS' RESEARCH PRIZE." Syllabuses with all information will be sent on application to the A Prize of £50 will be awarded in October to a past or present Sales SECRETARY.

of the School who, during the current year (October to atcexr) as to

the most valuable contribution to Tropical Medicine. The la: of the as EAST LONDON TECHNICAL

having already been published will not disqualify.

Contributions must be written in English.
COLLEGE

Essays must be sent in on or before October I next to the Vedi al Tar

who will be glad to afford further information. SENIOR ENTRANCE SCHOLARSHIPS.

London School of Tropical Medicine,

Royal Albert Dock, E.
The Drapers' Company propose to a ward in June, 1905, Six Senior

February, 1905.
Entrance Scholarships of the value of £40-three for boys and three for
girls between 16 and 19 years of age-enable at the East London Technical
College, Mile End Road, for three years. The Scholarships will be awarded

THE VICTORIA on the result of an examination to be held by the London Inter-Collegiate Scholarships' Board, full particulars of which, with forms of entry, may be UNIVERSITY OF MANCHESTER obtained from the SECRETARY of the Board, King's College, London, W.C.

FACULTY of MEDICINE
JUNIOR ENTRANCE SCHOLARSHIPS.

(including the DENTAL, PHARMACEUTICAL and Pr'YIC The Drapers' Company also offer for competition Ten Junior Entrance

HEALTH DEPARTMENTS). Scholarships, which, in addition to the money value, will entitle the holders The SUMMER SESSION will commence on Tuesday, April 15 to exemption from the College tuition fees, value gis first year, 623 second registration of Students will begin on this day at 9.3um year, and £30 third year. Candidates must be between 15 and 16 years of continued during the week (Saturday excepted). age on September 1, 1905. These Scholarships will be awarded on the London County Council Intermediate Scholarships Examination in May

PROSPECTUSES, giving full information as to coutin strahy

the MEDICAL and DENTAL DEGREES and DIPLOMAN The qualifications of means and residence attached to the Council's

will be forwarded on application to the Registrar. Scholarships will not apply to the Company's Scholarships. Forms of entry may be obtained from the CLERK to the Drapers' Company, Drapers' Hall, Throgmorton Street, E.C.

For other Scholastic Advertisements, seegy csaje.

next.

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MICROSCOPY.

with

net.

Just Published.

ELEMENTARY 3.

Pp. xii + 179

78 By F. SHILLINGTON SCALES, F.M.S.

Illustrations. "This is an admirable work containing exactly the information required by everyone who has occasion to use the microscope as an instrument of research. The volume contains much that ought to be, but is not, known to many who regard themselves as expert microscopists, and a more practical handbook on the microscope does not exist."-Pharmaceutical Journal.

London : BAILLIÈRE, TINDALL AND cox, 8 Henrietta Street, Covent Garden.

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The Official Organ of the British Electrotherapeutic Society.

TO SCIENTIFIC MEN ABROAD

MEDICAL ELECTROLOGY

AND RADIOLOGY,

AN INTERNATIONAL MONTHLY REVIEW COVERING

ALL BRANCHES OF ELECTROTHERAPEUTICS. Subscription, 12/- per Annum, Post Free throughout the World.

Single Numbers, 1/- ; Post Free, 1/2. LONDON : A. SIEGLE, 2 LANGHAM PLACE, 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. DAVID NUTT, 57-59 Long Acre, London, W.C.

Importer of Foreign Literature and Publisher. All FOREIGN WORKS reviewed in Nature are on sale or can be procured at shortest notice from David Nitt, at Continental l'rices.

SUBSCRIPTIONS can be effected through DAVID Nutt to all FOREIGN PERIODICALS.

RARE and OUT OF PRINT FOREIGN WORKS sought for with. out charge, and supplied at the most moderate prices. SECONDHAND FOREIGN CATALOGUES supplied regularly on demand, and orders executed therefrom.

English Books (New and Second-hand) and Periodicals promptly supplied at lowest rates. German and French Banknotes and Stamps received in payment. References

in all parts of the world. W. MULLER, Export Bookseller, London, W.

59 CASTLE STREET EAST, OXFORD STREET. SCIENTIFIC AND

EDUCATIONAL BOOKS NEW & SECOND HAND. LARGEST STOCK in LONDON of SECOND. HAND School, Classical, Mechanical, ELEMEN. TARY and ADVANCED SCIENTIFIC BOOKS

at about HALF PUBLISHED PRICE. Mathematical, Theological, and Foreign Books.

KEYS AND TRANSLATIONS.
J. POOLE & CO.

(EstaBLISHED 1854),
104 CHARING CROSS ROAD,

LONDON, W.C. (Formerly of 39 HOLYWELL STREET, STRAND).

Enquiries by letter receive immediate attention.

Sales by Auction..

LONDON (ROYAL FREE HOSPITAL) WANTED, by the Lancashire Education SCHOOL OF MEDICINE FOR WOMEN. Committee for the Dairy School, Hutton, near Preston, Lecturer on

Dairy Bacteriology and Practical Dairying from May 23 to Septemba if, 8 HUNTER STREET, BRUNSWICK SQUARE, W.C. 1905: Salary at the rate of 44 per week. Appliclums and copies o The SUMMER SESSION will begin on May 2, 1905.

Students

testimonials to be sent in not later than May I to the DIRECTOE entering on that date can compete for the Entrance Scholarships awarded

op EDUCATION, County Offices, Preston. in October. Special classes are arranged for the Preliminary Scientific and M.B. Examinations of the University of London.

SCIENCE MISTRESS required for Public Particulars as to fees, scholarships, &c., can be obtained from the

School in London. Degree or University Honours essential. Ne SECRETAKY, Miss Douie, MB J. A. H. COCK, M.D., Dean.

es., £130. Apply Mr. TRUMAN'S EDUCATIONAL AGENCY, & Holles Street, Cavendish Square, London, W. No fee is charged anless a:

engagement be secured through this Agency, when the cruis ar TUITION BY

reasonable. CORRESPONDENCE.

Vacation employment required by Analyst,

Ph.D., F.I.C. Used to lea hing and to literary work of sciemisc For MATRICULATION, B.A., SCHOLARSHIPS, and PRO

character, also to typewriting, photography, glass-blowing, and FESSIONAL PRELIMINARIES. Tuition in Latin, Greek, French,

research. Own appliances. Small remuneration sccepted. Easter to German, Italian, Mathematics, Mechanics, Physics, Chemis

July.-Apply " Beta," clo NATURE. try, Psychology, Logic, Political Economy, Book-keeping: The Staff includes Graduates of Oxford, Cambridge, London, and Royal Universities. --Address Mr. J. CHARLESTON, B.A , Burlington Currespond. FOR SALE.-X-Rays Outfit. 10" Apps Coil, ence College, Clapbam Common, London, S.W.

6 "Q21" accumulators, stand, tubes, sundries, in good working order.

Also 6" Apps Coil and 6" Harvey and Peak Coil. Can be seen by EGYPTIAN GOVERNMENT

appointment, London Stereoscopic Company, 54 Cheapeide. SCHOOLS.

For Sale.--"Nature," 1903, 1904, 1905 (to date), In view of the extension of Secondary Education in Egypt, applications

and pine numbers 1902. Offers to “ R.," c/o NATURE. are invited for new ASSISTANT-MASTERSHIPS in Secondary Schools under Ministry of Public Instruction. Masters to begin work in September, in Cairo or Alexandria, and to teach in English exclusively. Over 400 boys TYPE-WRITING UNDERTAKEN BY in each school, mainly Mohammedans. In the case of one of the Masters now required, the subject mainly essential is Science (Experimental Physics

HIGHLY EDUCATED WOMEN ACCUSTOMED TO SCIEN and Chemistry); six of the new Masters will be principally engaged in

TIFIC MSS. (Classical Tripos, Intermediate Arts, Cambridge Highe teaching Mathematics (Arithmetic, Geometry, and Algebra); the others will

Local, thorough acquaintance with Modern Languages). Rescuro, be concerned more particularly with the teaching of English. Candidates

Revision, Translation. Scale of charges on application. The Cam must be not less than 23 nor over 30 years of age, have a robust constitution,

bridge Type-writing Agency, 10 Duke Street, Adelphi, W.C. and have taken a University Degree in Honours. They must have ex. perience as Teachers : preference will be given to applicants who hold a Diploma in Teaching." Salary, £295 per annum (LEg.24 per mensem), rising to 6393 per annum (Leg.32 per mensem). Allowance for passage out to Egypt. Teaching hours, on an average, four daily, Fridays only excepted. Summer vacation not less than two months.

Applications, with full statement of qualifications, and accompanied by copies only of testimonials, must be sent in before May 15, 1905, marked

PALL MALL. outside Assistant Masterships,” and addressed to the SECRETARY: General, Ministry of Public Instruction, Cairo, Egypt, to whom candidates may apply for further information.

On View.- The Collection of Minerals of the late

JOHN HAWKINS. SCHOOL OF AGRICULTURE,

MESSRS. FOSTER respectfully announce GHIZEH, EGYPT.

for SALE by AUCTION, at the Gallery, 54 Pall Mall, JUNIOR LECTURER IN AGRICULTURE.

to-morrow, Friday, April 14, at I o'clock precisely, Applications are invited for the post of JUNIOR LECTURER in PART of the extensive and valuable COLLECTION AGRICULTURE at the School of Agriculture, Ghizeh, under the Ministry of Public Instruction.

of MINERALS, including fine specimens of Cornish Candidates must be not less than 23 nor over 33 years of age, have a Uranites, Cuprites, Liroconites, &c., Gold Specimens and robust constitution, and possess a University Degree or College Diploma in Agriculture. Preference will be given to applicants having experience of

Chalcedonies, also several well-made Cabinets. Agricultural Practice and Teaching. In addition to Agriculture, the Lecturer appointed will be required to teach elementary Agricultural May be viewed and Catalogues had, 54 Pall Mall. Botany and Entomology.

Salary, £295 per annum (4Eg.24 per mensem), rising to £393 per annum (£Eg:32 per mensem). Allowance for passage out to Egypt. Applications, with full statement of qualifications, and accompanied by

NATURAL HISTORY SPECIMENS. copies only of testimonials, must be sent in before May 4, 1905, 1o W. C.

TUESDAY, APRIL 18, at 13.30. MACKENZIE, Esq., D.Sc., Principal, School of Agriculture, Ghizeb, Egypt, to whom candidates may apply for further information.

MR. J. C. STEVENS will offer at his

Rooms, 38 King Street, Covent Garden, London, W.C., Rare and UNIVERSITY COLLEGE OF WALES,

Valuable Birds' Eggs; Entomological Specimens, British and Exotis:

Fine Cabinets, Books, Heads and Horns of Big Game, Fine Lion and ABERYSTWYTH.

Tiger Skins, and many general specimens. The COUNCIL invites applications for the post of REGISTRAR and

Catalogues and all particulars on application. SECRETARY of the COLLEGE, at a Salary of £300.

Applications and 70 copies of Testimonials to be sent by May 10 to the undersigned, from whom further particulars may be obtained.

T. F. ROBERTS, Principal. TO SCIENCE AND MATHEMATICAL

THE LARGEST MAKER IN ENGLAND MASTERS.--Required (1) for important Grammar School

of Apparatus in all Departments of London, Master for Physics and Mathematics. Salary, 6130, non-res. (2) Graduate qualified to teach Mathematics. $120. School in Lon. don. (3) Mathematical Master for Public School, Sea-side. £150. (4) Science and Maths. £100, resident. Army Coaching Establishment. (5) Mathematics and English, Wanted in September. 4100, including Radiography, High Frequency, Hydro-Electric and resident. Grammar School. - For particulars of above and other Science Light Baths, Finsen and other Light, Cautery, Electrolysis, &e. and Mathl. posts, address Griffiths, Smith, Powell & Smith,

Tutorial Agents (Estd. 1833), 34 Bedford Street, Strand, London. INDUCTION COILS AND STATIC MACHINES A SPECIALITY. APPLICATIONS are invited for the First

CONTRACTOR TO THE WAR Office, INDIA OFFICE, AND ADMIRALTY,

BRITISH AND FOREIGN HOSPITALS, &c.
European Professorship (Physics) at Meerut College, Northern India.
Salary, 6320 per annum 450 passage-money). Candidates should be

LISTS ON APPLICATION. University graduates, under 30 years of age, and unmarried. For particulars apply to Professor WORTHINGTON, Mohuns, Tavistock. 82 HATTON GARDEN, LONDON .

ALFRED E. DEAN,

near

ELECTRO-THERAPEUTICS

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MARBLE REDUCED TO QUICKLIME IN

10 MINUTES

with our NEW BLAST WARNING.

BUNSEN BURNER AND Observe that the

MIDGET FURNACE. Regulator of

We make these in two sizes at Burner, Body of

present, "" and ", and the prices Furnace, and

are-Burners only, 1/6 and 2/6; Hood are all dis.

complete with Furnace, 4/6 and tinctly stamped

6/in the metal

The consumption of gas is the “BREWSTER,

same as with an ordinary Bunsen, SMITH & Co.,

but the heat derived' is three LONDON."

times as great, and a number of Beware of imita

interesting experiments can be tions that do not

performed with them, which contain the essen.

have only been possible before tial feature of this

with very expensive furnaces. burner's success.

We are the SOLE MAKERS. 1 Nature says :-"The combination of furnace and burner is very convenient. These little furnaces are not only useful for reducing calcium carbonate to lime, but also work very well in fusion experiments.' BREWSTER, SMITH & CO., 6 CROSS ST., FINSBURY PAVEMENT, LONDON. Makers and importers of every description of Scientific

Apparatus and Chemicals. LABORATORIES FITTED & FURNISHED THROUGHOUT. Our NEW CHEMICAL APPARATUS LIST post free, 1/

Gratis to Colleges and Laboratories.

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SECOND-HAND

APPARATUS

ELECTRICAL AND PHYSICAL

BY STANDARD MAKERS, IN PERFECT WORKING ORDER, AT

EXTREMELY MODERATE TRICES. As supplied to the National Physicil Laboratory; Aberdeen, Aberystwyth, Birmingham, Nottingham and Glasgow Universities ; Bedford, Bradford, Clifton, Heriot Watt and Yorkshire Colleges; and twenty other Scientific

Institutions, Polytechnics, &c. IT NATURE says: “Teachers requiring efficient apparatus at a low co it for lecture or laboratory purposes, might consult the list with advantage."

List on application by mentioning Nature.

SECOND-HAND TELESCOPES. 6 in. Dallmeyer Equatorial, Clock, complete, £100. s} in. Alvan Clark, Equatorial by Cooke, £50. Several 3 in. Student Telescopes, by

leading makers, £4 10s., £6 10s., £8 10s., £10. SECOND-HAND SPECTROSCOPES, Single, 2, and 3 Prism, by Browning, £4 10s., £8 10s., £10.

SECOND-HAND MICROSCOPES. Watson's Edinburgh H., 3 powers and fittings, complete, as new, £16 10s. Swift Army Bacteria, complete, £15. Leitz 2b, with rack,

substage, and fittings, £6 10s. MANY OTHERS, ALL KINDS. LISTS ON APPLICATION. A. CLARKSON

CO., 28 BARTLETT'S BUILDINGS, HOLBORN CIRCUS, LONDON.

(Late MOTTERSHEAD & CO.),

FREDK. JACKSON & Co. 14 CROSS STREET, MANCHESTER LABORATORY FURNISHERS,

Goods Entrance : 10 Half-Moon Street.

Apparatus for estimation of sulphur in speot oxide.

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Importers, Manufacturers, and Dealers in
CHEMICAL AND PHYSICAL

APPARATUS
Of every Description.
Fine Chemicals, Volumetric Solutions,

Plain and Stoppered Bottles,
AND EVERY LABORATORY REQUIREMENT.
Illustrated Catalogue of Apparatus, with Price

List of Chemicals, free on application.
Telegraphic Address—"APPARATUS, MANCHESTER.'

Telephone Number-7238. MICROSCOPIC SLIDES. MARINE OBJECTS, Hydrozoa extended without pressure, sponge sections, &c. Apply for Lists.

Dispersal of Mr. HORNELL'S collection. Flower and Leaf Buds, Stems, Roots, &c., new, from zid. each. Lists.

Exhibition Groups of Diatoms, &c, in symmetrical patterns. EDINBURGH'H., by Watson, for sale, and others : several Objectives, Condensers, &c. PRISMATIC BINOCULARS, LANTERN SLIDES, Church Architecture, Swiss, Egypt and Holy Land views, all first class.

Fine mounted collection of Grasses, Mosses, Ferns, Marine Algæ.
Detailed List sent on application, as stock is always changing.
Mr. HERBERT CLARKE, 104 LEADENHALL STREET, E.C.

Tel. :-1316 CENTRAL.
With 30 Original Illustrations. Price 25. 6d.
The HYGIENE of the MOUTH.
A Guide to the Provention and Control of Dental Diseases.
By R. DENISON PEDLEY, L.D.S. Eng., F.R.C.S. Ed.,
Dental Surgeon to the Evelina Hospital, Southwark.

BY THE SAME AUTHOR.
The DISEASES OF CHILDREN'S TEETH

Well Illustrated. Price 75. 6d.
SEGG & CO., 289 and 291 Regent Street, London W.

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