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WAVE-LENGTH SPECTROSCOPE

(LARGE MODEL.)

Measures wave-lengths direct to an accuracy of 1 Ångström unit (one ten-millionth
of a millimetre) from W.L. 3888 to W.L. 7724.

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SPECIAL ADVANTAGES.

The Collimator and Telescope are rigidly fixed at right angles, thus the instrument will stand in a corner, is always ready for use and in adjustment.

The wave-lengths can be read off by the observer without moving from his place.

The object glasses and prism are large (1" clear aperture), which enables the faintest visible lines to be seen.

The eyepiece has a bright pointer for measuring the W. L. of bright lines on a dark field.

Means are supplied of very simply setting the Zero, although on account of the great rigidity and careful construction throughout it may be used for many months without any setting being needed.

ADAM HILGER, Ltd., 75a Camden Road, London, N.W.

AWARDED GOLD MEDAL ST. LOUIS EXHIBITION, 1904.
Telegraphic Address:-"Sphericity, London."

ILLUSTRATED LIST ("A") OF SPECTROSCOPES AND SPECTROSCOPIC ACCESSORIES
GRATIS ON APPLICATION.

THRELFALL

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MACMILLAN & CO.'S NEW BOOKS.

THE LIFE & EXPERIENCES OF

Sir Henry Roscoe, D.C.L., LL.D., F.R.S.

With Photogravure Portraits and other Illustrations. 8vo. 125. net.

Written by Himself.

THE GARTER MISSION TO JAPAN. By LORD REDESDALE, G.C.V.O., K.C.B.,

Crown 8vo. 6s.

Author of Tales of Old Japan." Extra

TIMES. -"Much has been written, and not a little well written, about Japan of recent years. But nothing has been better written than this tale of New Japan by the distinguished author of Tales of Old Japan.'

HIGHWAYS AND BYWAYS SERIES.-New Volume.

Illustrated by JOSEPH PENNELL

Extra Crown 8vo. 6s.

DORSET. By Sir FREDERICK TREVES, Bart., G.C.V.O., C.B.,

LL.D.

STANDARD.-" A breezy, delightful book, full of sidelights on men and manners, and quick in the interpretation of all the half-inarticulate lore of the countryside."

A SYSTEM OF APPLIED OPTICS. Being a Complete System of Formula of the Second

of the Third Order, with Examples of their Practical Application. T. Cooke and Sons, Ltd., of London, York, and Cape Town. 4to.

Order, and the Foundation of a Complete System By H. DENNIS TAYLOR, Optical Manager to 30s. net.

NEW WORK ON ASTRONOMY BY SIMON NEWCOMB.

A COMPENDIUM OF SPHERICAL ASTRONOMY.

With its Applica tions to the Deter

mination and Reduction of Positions of the Fixed Stars. By SIMON NEWCOMB. 8vo. 12s. 6d. net.

AN INTRODUCTION TO ASTRONOMY. By FOREST RAY MOULTON, Ph.D.

Illustrated. Crown 8vo.

5s. net.

CHEMISTRY OF THE PROTEIDS. By GUSTAV MANN, M.D. (Edin.), B.Sc.

(Oxon.), University Demonstrator of Physiology, Oxford. Based on Professor Otto Cohnheim's "Chemie der Eiweisskörper." 8vo. 155. net. NATURE.—“Its many excellences can be discovered by reading it and using it, and Dr. Mann is to be congratulated on having produced such a valuable addition to scientific literature."

PRACTICAL EXERCISES IN CHEMISTRY. By G. C. DONINGTON, M.A..

Grammar School. Globe 8vo. 2s. 6d.

Senior Science Master of Leeds

All the subjects included in the new syllabus in Chemistry for the Matriculation Examination of the University of London are dealt with in this book.

For the New Syllabus of the Preliminary Examination for the Certificate (1907).

LESSONS IN SCIENCE. A Preliminary Course of Physics and Chemistry. By Professor R. A.

GREGORY and A. T. SIMMONS, B.Sc. Illustrated.

THE BIOLOGY OF THE FROG.

Crown 8vo. 6s. 6d. net.

A MANUAL OF GEOMETRY.

35. 6d.

By SAMUEL J. HOLMES, Ph.D., Assistant Professor of Zoology in the University of Wisconsin. Illustrated.

By W. D. EGGAR, M.A., Assistant Master at Eton College.
Crown 8vo.
3s. 6d.

An experimental treatment of Geometry, in which Theorems are taken along with the practical work. NATURE.--" We know of no text-book of elementary geometry which can be more confidently recommended to teachers, and none from which students are likely to derive more profit.'

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THE BEGINNER'S SET OF MATHEMATICAL INSTRU

MENTS. Bow Compass; Dividers; Two Nickel Set Squares (45° and 60° respectively), 4 inches and 5 inches long, two edges of which show inches and tenths and millimetres; Nickel Protractor; double bevelled 6-inch Rule showing inches and tenths and millimetres; and a Lead Pencil. All enclosed in Metal Pocket-Case. Is. 6d. net.

THE DYNAMICS OF LIVING MATTER.

By Professor JACQUES LOEB.
Svo. 12s. 6d. net.

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WATKINS & DONCASTER,

Naturalists and Manufacturers of CABINETS AND APPARATUS

FOR ENTOMOLOGY, BIRDS EGGS AND SKINS, AND ALL
BRANCHES OF NATURAL HISTORY.

SPECIAL SHOW-ROOM FOR CABINETS.
N.B.-For Excellence and Superiority of Cabinets and Apparatus, refer-
ences are permitted to distinguished patrons, Museums, Colleges, &c.
A LARGE STOCK OF INSECTS, BIRDS' EGGS AND SKINS.
SPECIALITY.-Objects for Nature Study, Drawing
Classes, &c.

Birds, Mammals, &c., Preserved and Mounted by First-class Workmen true to Nature.

All Books and Publications on Natural History supplied. 36 STRAND, LONDON, W.C. (Five Doors from Charing Cross-)

CATALOGUE (102 pp.) POST FREE.

SAVAGE CURIOSITIES.
ETHNOGRAPHICAL SPECIMENS.

Stock of over 10,000 Specimens of Weapons, Implements, Ornaments,
Dress, Idols, Musical Instruments, &c. &c., used by all the Races of
Mankind, for sale at very lone prices. All objects guaranteed genuine.
Trophies of genuine out Arms made for Biard Rooms, Halls, &c.,
prices from 254.; also mounted Hors-Catalogue of Ethnographical
Specimens Llustrated with Bromide Photographs, ad monthly, 35. 6d.
yearly. Collections Arranged and Catalogued. Specimens bought.
W. O. OLDMAN. 77 BRIXTON HILL, LONDON, S.W.

Minerals, Rocks, Fossils, Metallic Ores, Rough Precious Stones, &c.

A Large Assortment from all parts of the world alway, on view, and at al prices. Inspect.ca invited.

Crude Mineral for Chemistry Students and Technical Schools. Single Crystals and Teaching Specimens in Great Variety. RICHARDS SHOW ROOMS,

3 Beauchamp Place, Brompton Road, South Kensington, London, S.W.

LIVING SPECIMENS FOR

THE MICROSCOPE.

Valvos, Spirogyra, Desmids, Diatoms, Amreba, Arcella. Actinospherium, rticala, Stentor, Hydra, Foscularia, Stephanoceros, Melicerta, and many ather specimens of Pond Life Price per Tube, Post Free. Herz pomatia, Astacus, Amphioxus, Rana, Anodon, &c. for Dissection purposes. THOMAS BOLTON,

25 BALSALL HEATH ROAD, BIRMINGHAM.

MARINE BIOLOGICAL ASSOCIATION
OF THE UNITED KINGDOM.
THE LABORATORY, PLYMOUTH.
The following animais can always be supplied, either living
or preserved by the best methods:-
Sycow Clava Cheia, Sertularia; Ana Tealia. Caryophylia. A.c7-
, Hampura preserved). Leptoplana Lineas Anpc.ports.
Nerets. Apurodite
Lanice. Terepeila Lepas Balanus,
Cammaris. Liga Ms. Nealia. Caronus Parella. Baconum. Redone,
Pectens Bugia Crissa, Pedicelina. Hasthuria. Asterias, Echinus,
Asoria Saca preserves, Scylinn. Raa &c. &c.
Far prices and nare tetanet ists apply to
Bisogca Lancratory. Plymouth.

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THE DIRECTOR.

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CHAR CES FR ADVERTISEMENTS

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11:ney Orions pays EACHILLAT Limited.

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The "INCANDANODE" TUBE

(so called because it works all day with the Anode RED HOT). This Tube ran from 9 a.m. to 6 p.m. for five days at the Leicester meeting of the B. M.A. last July. The Anode was incandescent the whole time, but the Vacuum was fully maintained. One Tube will last for years. The Vacuum is easily adjustable.

THE

BELOT SHIELD FOR X-RAY
WORKERS.

MR. HALL EDWARDS (at the Leicester meeting of the B. M. A. last July) said of this shield: It is a scientific instrument designed on scientific lines, and overcomes all the objections which exist in the shields previously brought to my notice."

THE

MEDICAL SUPPLY ASSOCIATION, 228 GRAY'S INN ROAD, LONDON, W.C. Descriptive Circulars (with expert testimony) on application.

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SPINTHARISCOPES.

(As devised by Sir WM. CROOKES.)

Showing the Scintillations of Radium. Fitted with powerful Lens, and contained in neat Leather Case.
Price 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 Pitchblende or any other radio-active substance.

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See letter from Prof. Gotch on "The Spinthariscope and Retinal Excitability" (NATURE, June 22, 1905, page 174), setting forth a valuable scientific application of the instrument.

Calcium Metal

15/- per lb. 11/3 per oz.

Thorianite
4/- per oz.
Radium Bromide from £16 per 5 mgs.

A. C. COSSOR, 54 Farringdon Road,

Telephone No. 10547 Central.

THE

LONDON, E.C.

Awarded Gold and

Silver Medals at
St. Louis Exhibition.

STIGMATIC LENS.

BRITISH

SERIES II. F/6.

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DESIGN AND WORKMANSHIP.

Is the best All-round Lens for either Professional or Amateur use.
Each lens will give perfect definition with full aperture to the extreme corners of the plate
it is sold to cover; with smaller stops it will cover at least two sizes larger, giving perfect sharp-
ness all over the plate, and thus becoming a wide-angle lens of the highest excellence. Either
combination may be used separately, giving foci of about 1 and 2 times the length of that of
the lens when used intact. The advantage of thus being able to choose the best point of view,
irrespective of distance, will be at once apparent to the artistic worker.

EQUIVALENT TO FOUR LENSES AT THE PRICE OF ONE.
Eleven Sizes are now ready, from 3 to 18 inches eq. focus.

CATALOGUE OF HIGH-CLASS CAMERAS AND LENSES, POST FREE.

J. H. DALLMEYER, Ltd., 25 NEWMAN ST., OXFORD ST., LONDON, W.

MAKERS OF THE CELEBRATED DALLMEYER LENSES.

Frinted by RICHARD CLAY AND SONS, LIMITED, at & Lead Street Hil, Queen Victoria Street, In the Cit. of Lain by MAA

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