WORKS BY JOHN TYNDALL, LL.D. F.R.S. Professor of Natural Philosophy in the Royal Institution of NOTES OF A COURSE OF NINE LECTURES ON LIGHT, Delivered at the Royal Institution of Great Britain, A.D. 1869. Crown 8vo. price 18. sewed, or 1s. 6d. cloth. NOTES OF A COURSE OF SEVEN LECTURES ON Delivered at the Royal Institution of Great Britain, A.D. 1870. ON RADIATION: Crown 8vo. The Rede Lectures delivered before the University of Cambridge, a.d. 1865. ON THE SCIENTIFIC USE OF THE IMAGINATION; A Discourse delivered before the British Association for the Advancement of HEAT A MODE OF MOTION. Fourth Edition, with Alterations and Additions. Plate and 108 Woodcuts. SOUND; A Course of Eight Lectures delivered at the Royal Institution of Great Britain. FARADAY AS A DISCOVERER. New and Cheaper Edition, with Two Portraits. Fcp. 8vo. price 3s. 6d. RESEARCHES ON DIAMAGNETISM AND MAGNE CRYSTALLIC ACTION; Including the question of Diamagnetic Polarity. With Six Copper Plates and numerous Woodcut Illustrations. 8vo. price 148. DR. FARADAY, by a series of inductive researches of the most perfect character, established DIAMAGNETISM as a force of almost universal influence upon matter, but possessing principles which broadly distinguished it from that magnetism which peculiarly belongs to iron, but which is manifested in a less degree by some three or four other metals. M. PLUCKER discovered the action of a magnet upon crystallised bodies, and gave the name of Magne-crystallic force to it, finding it to be distinct from either Magnetism or Diamagnetism by its giving a determined position to the mass under its influence. M. PLUCKER's investigations led him to believe that the direction assumed by a crystal under magnetic influence was determined by the optic axis of the crystal; and Dr. FARADAY, concurring in this view, called it the optic axis force. Dr. TYNDALL took up the inquiry at this point, and was led to a somewhat different conclusion. He appeared to prove that the position of the optic axis is not necessarily the line of magne-crystallic force, and that the force which determined the position of the optic axis in the magnetic field was not independent of the magnetism or diamagnetism of the mass of the crystal. Beyond this Dr. TYNDALL has shewn that the lines of cleavage seem to influence the position of the crystal in the magnetic field, as they will be axial in a magnetic and equatorial in a diamagnetic crystal; and everything that tends to destroy the cleavages tends also to destroy the directive power. This volume is devoted to a republication of the papers in which these important researches were recorded... There are many advantages in thus collecting together a set of researches of this nature. We have now in a collected form. for the use of the scientific student, a record of the experimental evidence upon which the conclusions above referred to are based. The book is plentifully illustrated with carefully-drawn woodcuts, which will be found of great use to those who may desire to investigate further those magnetic phenomena which appear to lead to an eluci dation of the mysteries involved in the atomic constitution of matter." ATHENAEUM. London: LONGMANS, GREEN, and CO. Paternoster Row. INDUCTION COILS, ELECTRIC TELEGRAPHS, & BELLS. J. & W. RICKARD, SILK MANUFACTURERS, DERBY, Manufacture and Supply for above purposes all sizes and quantities of Silk or Cotton covered INSULATED COPPER WIRE CONDUCTIVITY GUARANTEED NINETY-FIVE PER CENT. NEW WORKS BY WILLIAM CROOKES, F.R.S. www Preparing for publication, SELECT METHODS IN CHEMICAL ANALYSIS AND By WILLIAM CROOKES, F.R.S. &c. Editor of "The Chemical News.' A HANDBOOK OF DYEING AND CALICO PRINTING. London: LONGMANS, GREEN, and CO. Paternoster Row. Nearly ready, in ONE VOLUME Crown 8vo. with COLOURED PLATES and other SPECTRUM ANALYSIS IN ITS APPLICATION TO TERRESTRIAL SUBSTANCES AND THE PHYSICAL CONSTITUTION OF THE HEAVENLY BODIES, Familiarly Explained by Dr. H. SCHELLEN, Director der Realschule I. O. Cologne. Translated from the German by the Misses LASSELL; edited, with Notes, by WILLIAM HUGGINS, LL.D. D.C.L. F.R.S. London: LONGMANS, GREEN, and CO. Paternoster Row. Just published, in SMALL FOLIO, price 25s. cloth, PROCTOR'S (R. A.) NEW STAR ATLAS, in Twelve Circular Maps, 13in. diameter, containing ALL the STARS visible to the naked eye and about 1,500 Objects of Interest, viz. Red Stars, Double Stars, &c. Photolithographed by A. BROTHERS, F.R.A.S. With Two INDEX PLATES and a Letterpress Introduction. 'I like the specimen-map very much. The distortion is so small as to obviate all doubt or inconvenience in comparing the chart with the sky. I have no objection to your mentioning my high approval of this work.'-From a Letter by SIR J. HERSCHEL. London: LONGMANS, GREEN, and CO. Paternoster Row. Just published, crown 8vo. cloth, price 78. 6d. THE MANUAL OF COLOURS AND DYE WARES: THEIR PROPERTIES, APPLICATIONS, VALUATION, IMPURITIES, AND SOPHISTICATIONS. FOR THE USE OF DYERS, PRINTERS, DRY SALTERS, BROKERS, &c. By J. W. SLATER, Author of The Handbook of Chemical Analysis for Practical Men.' LOCKWOOD and CO., 7 Stationers'-Hall Court, Ludgate Hill, E.C. BROWNING'S NEW LARGE AUTOMATIC ELECTRIC LAMP. In this Lamp both carbons are moved by the electricity of the battery employed (without the aid of clockwork); the light remains uniform in height, and more steady in action than any of the expensive regulators previously introduced. Any number from 20 to 50 quart Grove's Cells, or 2 quart Bunsen's, may be used with this Lamp. Price £8 8s. JOHN BROWNING begs to announce that he has prepared, with peculiar care, a great number of Diagrams, to illustrate recent discoveries in Spectrum Analysis and other branches of Observational Astronomy. These Slides can be had either plain or exquisitely coloured. Prices 3s. 6d. plain, and from 4s. 6d. to 10s. 6d. coloured. A list of subjects priced on application. Photographs of Microscopic Objects for the Lantern, 3s. each. Lists on application. ELECTRIC LAMPS, either separately or with Lantern Apparatus, for Public Exhibitions and Lectures, for showing Diagrams or Spectrum Experiments on Screen, or for Illuminating Halls or Buildings, on hire, either in town or country. Qualified Assistants sent if desired. Terms on application. JOHN BROWNING, OPTICAL AND PHYSICAL INSTRUMENT MAKER 111 MINORIES, LONDON, E. SPECTACLES SCIENTIFICALLY ADAPTED TO REMEDY WEAK OR DEFECTIVE VISION. ME being anxious that ESSRS. HORNE & THORNTHWAITE especial attention should be paid to the selection of Spectacles supplied by them, have great pleasure in announcing that Mr. WILLIAM ACKLAND, Surgeon (Registered under the Medical Act), may be consulted in all matters relative to Spectacles, daily, from 10 till 5, Saturdays, 10 till 1, at their establishment, 123 Newgate Street. MR. ACKLAND has, for the last 18 years, paid especial attention to the optical means necessary to remedy defective sight, and has also lately brought to perfection his improved form of Optometer used in adapting Spectacles, which is confidently asserted to be the only instrument known giving an exact knowledge of the foci and adjustment of the eye, and thus enabling even weak and defective sight to be supplied with suitable Spectacles. Sufferers from defective sight should read Ackland's Spectacles,' sent post free for seven stamps. HORNE & THORNTHWAITE, Hints on OPTICIANS TO THE QUEEN, 122 and 123 NEWGATE STREET, LONDON, E.C. 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