AN

IMPORTANT APPLICATION

of the

DUDDELL OSCILLOGRAPH

is the investigation of telephone

currents.

The photograph reproduced is taken from Mr. DUDDELL'S paper before the Royal Institution, March 16, 1906, on "How to improve Telephony." It shows the curve of the current produced in a telephone by the sound of "O" as in NO! The speed of the photographic plate was 250 cms. per second and the time reads from left to right.

Write for details and prices of outfits to

The Cambridge Scientific Instrument Co., Ltd.,

JAMES J. HICKS,

8, 9 & 10, HATTON GARDEN, LONDON, E.C., MAKER OF ALL KINDS OF STANDARD METEOROLOGICAL INSTRUMENTS Maker of Merral andAneroid Barometers of every description, also of Captain George's Barometer -Warkin Potest Ageros Clsuneters, and the famosa Bange Finders used by the War ue, Rygrometer for the packet and Hypometrinal Apparatus. Aloey set other Levels. Plane Tables, Rain Gauges and Outants and Theodotes, and Thermometers of all cints for c

HOLDER OF THE LARGEST STOCK OF CLINICAL THERMOMETERS IN THE WORLD

STANDARD BAROMETER, diameter of Tube, 0-5 in., on Mahogany Board..

KEW OBSERVATORY CERTIFICATES SUPPLIED IF DESIRED

STEREOSCOPIC

STAR SLIDES.

From Drawings by T. E. HEATH, F.R.A S, and exhibited by him at Royal Society and British Association. Projected with an ordinary single Lantern, the stars appear to shine at different distances from the screen. Very beautiful and attractive. 31" x 31", 6/- each, framed.

LARGE TRANSPARENCIES,

6" square, for Window Decoration, &c., 12/6 each.
Pair in Black Frame, 21/-

FULL DETAILS ON APPLICATION,

FLATTERS & GARNETT, Ltd., 48 DEANSGATE,

Laboratories:

Church Road, Longsight, Manchester

MANCHESTER.

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 low prices. All objects guaranteed genuine.
Trophies of genuine old Arms made for Billiard Rooms, Halls, &c.,
prices from 258.; also mounted Horns.- Catalogue of Ethnographical
Specimens illustrated with Bromide Photographs, ad. monthly, 3s. 6d.
yearly. Collections Arranged and Catalogued. Specimens bought.
W. O. OLDMAN, 77 BRIXTON HILL, LONDON, S.W.

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.

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

A Large Assortment from all parts of the world always on view, and at all prices. Inspection 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.

Collections and Single Specimens of
British and Foreign

MINERALS, ROCKS, FOSSILS.

25 Specimens, 5/6; 50 do., 10/6; 100 do., 21/-; 200 do., 42/-. 20 Coal Measure Rocks and Fossils, 12/6; do., larger, 15/-. In Polished Deal Boxes.

Inspection invited of a large stock of Minerals, Rocks, Fossils, and Microscopic Objects. Specimens sent on approval.

Cabinets, Geologists' Hammers, Card Trays, Glass-Capped Boxes, Models of Crystals, and other Apparatus for Geologists, &c. NEW CATALOGUES POST FREE.

THOMAS D. RUSSELL, 78 Newgate St., London, E.C.

LIVING SPECIMENS FOR

THE MICROSCOPE.

Helix

Volvox, Spirogyra, Desmids, Diatoms, Amoeba, Arcella, Actinos; bærium, Vorticella, Stentor, Hydra, Floscularia, Stephanoceros, Melicerta, and many other specimens of Pond Life. Price 1s. per Tube, Post Free. 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 animals can always be supplied, either living or preserved by the best methods :

Sycon; Clava, Obelia, Sertularia; Actinia, Tealia, Caryophyllia, Alcy. onium; Hormiphora (preserved); Leptoplana; Lineus, Amphiporus, Nereis, Aphrodite, Arenicola, Lanice, Terebella; Lepas, Balanus, Gammarus, Ligia Mysis, Nebalia, Carcinus; Patella, Buccinum, Eledone, Pectens Bugula, Crisia, Pedicellina, Holothuria, Asterias, Echinus, Ascidia, Salpa (preserved), Scyllium, Raia, &c., &c. For prices and more detailed lists apply to Biological Laboratory, Plymouth.

THE DIRECTOR.