illumination with that of the standard light. Experiment had shown that the sensitiveness of the instrument is greatest when the difference of the contrasted illuminations is 3 per cent., and amounts then to per cent. He further gave an account of experiments which he and Dr. Lummer had made on the utilization of glow-lamps as standards of comparison. When fed by accumulators these lamps yield a light which only varies by I per cent. during a period of 200 hours provided the E. M. F. of the accumulators is kept constant. The authors are now busy with the endeavour to construct a standard glow-lamp for comparison with unknown sources of light. Dr. Lummer demonstrated Abbé's apparatus for testing transparent films with planeparallel surfaces. After briefly describing the interference phenomena produced by thick plane-parallel glass plates, he explained how Tizeau's bands and Newton's rings are employed for testing the plates, using monochromatic sodium-light. The light passes through a reflecting prism and through a lens, and then falls on the plate, from which it is reflected and passes back by the same path to the eye, being now passed through a second lens by means of which the bands or rings may be seen. The occurrence of interference-bands is entirely dependent upon the thickness of the plate: if this is absolutely uniformly thick throughout, the interference phenomena show no change if the plate is moved from side to side in its own plane, and by so doing the parallelism of its sides may be rapidly tested.

Ce, La, Di: oxalic acid, ferrocyamide of potassium.

Zn, Ca: acetate of aluminium and oxalic acid.

Zn, Cn, Co: sulphocyanide of mercury and ammonium.

,, Co, Ni: nitrite of potassium and acetate of lead.

Pb, Bi, Fe: bichromate of potassium and potash.

Bi, Sb, Sn: oxalic acid, chloride of rubidium.

,, Sb, Sn, Ti: chloride of barium and oxalic acid. Details will soon be published, when the necessary finish has been given to the methods for separation, hitherto somewhat neglected.-M. Martin read a paper on the geology of the Kei Islands, and, in connection therewith, on the Australian-Asiatic boundary line. In accordance with the fact that in Great Kei we meet with nothing but a Tertiary formation, and that the nature of the rocks of Great Kei agrees with that of the coast of New Guinea, M. Martin inferred that this boundary line must be drawn geognostically, to the west of Great Kei and to the north-west of Timor.-Dr. Beyerinck treated of the luminous food and the plastic food of phosphorescent Bacteria. Of the six species of phosphorescent Bacteria hitherto known, four-viz. the alimental gelatine non-melting Bacterium phosphorescens and B. Pflügeri of luminous fish, and the Baltic phosphorescent Bacteria, B. Fischeri and B. balticum, require, besides peptone, a second carbonic combination, as glycerine, glucose, or asparagine, for their complete nourishment, i.e. to "phosphoresce and grow. They may be called peptone-carbon-bacteria. The gelatine quick-melting phosphorescent bacteria from the West Indian Sea and the North Sea, B. indicum and B. luminosum, can phosphoresce and grow on peptone alone. They are, therefore, peptone-bacteria. Again, other bacteria can derive their nitrogen either from amids, the amid-bacteria, or from ammoniac, the ammoniac-bacteria. Also moulds, yeasts, and Protozoa may be classed in this system. The Bacterium Pflügeri does emit light with peptone and glucose, but not with peptone and maltose, while the Bacterium phosphorescens emits light both with glucose and maltose. Now if we mix some starch in a phosphorescens-peptone-gelatine, obtained by mixing this gelatine with a very great number of B. phosphorescens, and place upon this some ptyaline, pancreas-diastase, or urindiastase (nefrozymase), fields of light make their appearance; if, however, we placed these same sorts of diastase on a Pflügeri-peptonestarch-gelatine, then no fields of light would appear, which

some

proves that in this instance no glucose whatever is formed, as was lately believed to be the case. The development of luminosity is constantly accompanied by the transition of peptones into organized, living matter, under the influence of free oxygen, with or without the concurrence of another carbonic combination.

BOOKS, PAMPHLETS, and SERIALS RECEIVED.

Among the Selkirk Glaciers: W. S. Green (Macmillan).-Flora Tangutica, fasc. i.: C. J. Maximowicz (Petropoli).-Enumeratio Plantarum Hucusque in Mongolia, fasc. i.: C. J. Maximowicz (Petropoli).-The Human Epic, Canto i.: J. F. Rowbotham (K. Paul).-Agende de Chimiste, Salet, Girard and Pabst (Hachette).-The Theory of Determinants in the Historical Order of its Development; Part i., Determinants in General: T. Muir (Macmillan). -The Microtomist's Vade-Mecum, 2nd Edition: A. B. Lee (Churchill).— Guide Pratique de L'Amateur Électricien: E. Keignart (Paris, Michelet).Musiconomia o Leggi Fondamentali della Scienza Musicale: P. Crotti (Parma, Battei).-L'Éclairage Électrique Actuel, 2nd Edition: J. Couture (Paris, Michelet).—Das Reizleitende Gewebesystem der Sinnpflanze: Dr. G. Haberlandt (Leipzig, Engelmann).-Traité Ency. de Photographie, 15 Mars: C. Fabre (Paris, Gauthier-Villars).-Proceedings of the Aristotelian Society, vol. i. No. 3, Part 1 (Williams and Norgate).-Mind, April (Williams and Norgate).-Geological Magazine, April (K. Paul).-Quarterly Journal of Microscopical Science, April (Churchill).-Journal of the Royal Agricultural Society of England, 3rd Series, Part 1 (Murray).—Journal of the Royal Horticultural Society, vol. xii. Part 1 (London).

HAND-BOOK OF MORAL PHILOSOPHY. By the Rev. Prof. HENRY CALDERWOOD, LL.D. Edition, largely re-written. Crown 8vo. 6s. SEEING AND THINKING. By the late Prof. W. K. CLIFFORD, F.R.S. With Diagrams. Crown 8vo. 35. 6d. [Nature Series.

ECONOMY. By Dr. LUIGI COSSA, Professor in the University of Pavia. Translated from the Second Italian Edition. With a Preface by W. STANLEY JEVONS, F.R.S. Crown 8vo. 4s. 6d.

INDIVIDUALISM: A System of Politics. By

WORDSWORTH DONISTHORPE. 8vo. 145.

ALFRED MARSHALL, M.A., Professor of Political Economy in the University of Cambridge, Fellow of St. John's College, Cambridge, sometime Fellow of Balliol College, Oxford. 2 vols. 8vo. Vol. I. shortly.

A DICTIONARY OF POLITICAL ECONOMY. By various Writers. Edited by R. H. INGLIS PALGRAVE.

[In the press. THE PRINCIPLES OF POLITICAL ECONOMY. By HENRY SIDGWICK, M.A., LL.D., Knightbridge Professor of Moral Philosophy in the University of Cambridge, &c., Author of The Methods of Ethics." Second Edition, Revised. 8vo. 165. THE ELEMENTS OF POLITICS. By the same [In the press. POLITICAL ECONOMY. BY FRANCIS A. WALKER, M.A., Ph. D. Second Edition, Revised and Enlarged. 8vo.

A

Author. 8vo.

12s. 6d.

BRIEF TEXT-BOOK OF POLITICAL ECONOMY. By the Same. Crown 8vo. 6s. 6d.

THE WAGES QUESTION. By the Same. 8vo. 14s. ALPHABET OF ECONOMIC SCIENCE.

By

PHILIP H. WICKSTEED, M.A. Part I.-Elements of the Theory of Value or Worth. Globe 8vo. 25. 6d. ·

on Logic and Scientific Method.
Revised Edition. Crown 8vo.

STUDIES IN DEDUCTIVE LOGIC. same Author. Second Edition. Crown 8vo. 6s.

CRITIQUE OF PURE REASON.

By the

By IMMANUEL KANT. In commemoration of the Centenary of its first Publication. Translated into English by F. MAX MÜLLER. With an Historical Introduction by LUDWIG NOIRE. 2 Vols. Demy 8vo 16s. each.

Vol. I. HISTORICAL INTRODUCTION, by LUDWIG NOIRÉ; &c.
Vol. II. CRITIQUE of PURE REASON, translated by F. MAX MÜLLER.
For the convenience of students these volumes are now sold separately.
KANT'S CRITICAL PHILOSOPHY FOR ENG-
LISH READERS. By Prof. JOHN P. MAHAFFY, D.D., and
JOHN H. BERNARD, B.D. A New and Completed Edition in 2
Vols. Crown 8vo.
Vol. I. THE KRITIK OF PURE REASON EXPLAINED AND
DEFENDED.
75. 6d.
Vol. II. THE "PROLEGOMENA."
Appendices. 65.

Translated, with Notes and

FORMAL LOGIC, Studies and Exercises in. Including a Generalization of Logical Processes in their Application to Complex Inferences. By JOHN NEVILLE KEYNES, M.A. Second Edition, Revised and Enlarged. Crown 8vo. 10s. 6d.

PSYCHOLOGY. BY JAMES McCosн, D.D., LL.D.,

Litt. D. Crown 8vo.

SIDGWICK, M.A., LL.D., Third Edition. 8vo. 145.

A SUPPLEMENT to the Second Edition, containing all the important Additions and Alterations in the Third Edition. Demy 8vo. 65. OUTLINES OF THE HISTORY OF ETHICS FOR ENGLISH READERS. By the same Author. Second Edition, Revised. Crown 8vo. 3s. 6d.

THE LOGIC OF CHANCE. An Essay on the Foundations and Province of the Theory of Probability with Special Reference to its Logical Bearings and its Application to Moral and Social Science. By JOHN VENN, M.A. Third Edition, Re-written and greatly Enlarged. Crown 8vo. 10s. 6d.

SYMBOLIC LOGIC. By the same Author. Crown

THE

LONDON HOSPITAL MEDICAL
COLLEGE.

The SUMMER SESSION will commence on THURSDAY, MAY 1. The Hospital, which is the largest general Hospital in the Kingdom, contains nearly 800 beds, all in constant use. There are wards for accidents, surgical and medical cases, diseases of women and children, and ophthalmic cases. Special departments for diseases of the eye, ear, throat, skin, and teeth, and for cancer, tumours, diseases of the bladder, piles, and fistula. Number of in-patients last year, 8873; out-patients, 101,548; accidents, 7456.

Surgical operations daily.

APPOINTMENTS.-Resident Accoucheur, House Physicians, House Surgeons, &c. Forty of these Appointments are made Annually. Numerous Dressers, Clinical Clerks, Post-mortem Clerks, and Maternity Assistants are appointed every Three Months All Appointments are Free. Holders of Resident Appointments are also provided Free Board. The New College Buildings are now complete, and afford more than double the former accommodation.

SCHOLARSHIPS AND PRIZES.-Twenty Scholarships and Prizes are given annually. Students entering in May are eligible to compete for the four Entrance Scholarships in September.

Luncheons or Dinners, at Moderate Charges, can be obtained in the Students' Club.

N.B.-Special arrangements have been made to meet the requirements of the Examining Board in England so as to enable Students entering in May to pass Part I. (Chemistry and Chemical Physics), and Part II. (Materia Medica and Pharmacy) of the First Examination in July.

The London Hospital is now in direct communication with all parts of the Metropolis. The Metropolitan District and other Railways have Stations within a Minute's Walk of the Hospital and College.

For further Information apply Personally or by Letter to
Mile End, E.

MUNRO SCOTT, Warden.

ST. THOMAS'S HOSPITAL MEDICAL

SCHOOL,

ALBERT EMBANKMENT, LONDON, S.E.

The SUMMER SESSION will commence on MAY 1. Students entering in the Summer are eligible to compete for the Science Scholarships of 125 Guineas and £60 awarded in October.

There are numerous Prizes and Scholarships, and all Appointments are open to Students, without extra charge.

Special Classes for the Examinations of the University of London are held throughout the year. A Register of approved lodgings, and of private families receiving Students to reside, is kept in the Secretary's Office. Prospectus and all particulars may be obtained from the Medical Secretary, Mr. G. RENDLE.

E. NETTLESHIP, Dean.

ST. MARY'S HOSPITAL MEDICAL

SCHOOL,

PADDINGTON, W.

Two ENTRANCE SCHOLARSHIPS of £50 each in Classics and Mathematic. will be awarded by Examination on APRIL 25, and in SEPTEMBER there will be an Examination for Entrance Scholarships in Natural Science.

There are Special Classes in preparation for the Examinations of the University of London.

The Prospectus and full Particulars may be had by applying to the School Secretary, Mr. FREDERIC H. MADDEN.

The Summer Session begins on MAY 1.

HERBERT W. PAGE, M.C., Dean.

LEEDS MECHANICS' INSTITUTION AND LITERARY SOCIETY.

The Directors invite applications for the post of HEAD MASTER of the SCHOOL OF SCIENCE AND TECHNOLOGY and TEACHER OF CHEMISTRY to the Boys' and Girls' Schools in connection with the Institution, the present Head Master having been elected to the Head Mastership of the Merchant Venturers' School, Bristol. The Master appointed will be expected to take the classes in Theoretical and Practical Inorganic and Organic Chemistry, and to exercise a general supervision over the other classes of the School of Science. The School buildings are new, and furnished with all necessary materials and apparatus for science teaching. Salary, partly fixed and partly dependent upon results, amounts to about £280. Full particulars may be had from the SECRETARY, to whom applications must be sent not later than April 23.

CAVENDISH COLLEGE, CAMBRIDGE.

An EXAMINATION will be held on TUESDAY, July 8, and following days, for One Scholarship of £50 and Six Scholarships of £30 a Year, open to Students under 18 Years on October 1, 1890. Candidates may offer one or more of the following Subjects;

Classics, Mathematics, Natural Science, Modern Languages.

The College Fee for Board, Lodging, and Tuition is £25 for each of the Three University Terms, and £15 for Residence in the Long Vacation. For further information apply to the MASTER.

WANTED, A Second-hand Astronomical

Telescope, in good condition.-Particulars to W. ASHMOLE, 2 Hainault Terrace, Ilford.

LIVING SPECIMENS FOR THE MICROSCOPE.

GOLD MEDAL awarded at the FISHERIES EXHIBITION to THOMAS BOLTON, 83 Camden Street, Birmingham, Who last week sent to his subscribers Paludicella Ehrenbergi, with sketch and description. He also sent out Lophopus crystallinus, Argulus foliaceus, Corethra. Trout Ova, Philodina roseola, Floscularia, Corethra plumicornis, Melicerta ringens, Stephanoceros; also Amoeba, Hydra, Vorticella, Crayfish, Dog-Fish, Amphioxus, and other Specimens for Biological Laboratory work. Weekly Announcements will be made in this place of organisms T. B. is supplying.

Specimen Tube, One Shilling, post free. Twenty-six Tubes in Course of Six Months for Subscription of £1 15., or Twelve Tubes for 10s. 6d.

Portfolio of Drawings, Eleven Parts, 1s. each.

ZOOLOGICAL SOCIETY OF LONDON. DAVIS LECTURES, 1890.

A Course of Six Lectures will be delivered in the Lecture Room in the Society's Gardens. Regent's Park, on THURSDAYS. at 5.30 p m., commencing THURSDAY, MAY 8, by Mr. F. E. BEDDARD, M.A., Prosector to the Society, and Davis Lecturer.

SUBJECT

THE COLOURS OF ANIMALS.

Fee for the Course (including admission to the Gardens on the days of Lectures), 5s.

The Course will be free to all Fellows of the Society. Tickets for the Course may be obtained from Mr. F. E. BEDDARD, Zoological Society's Gardens, Regent's Park, N.W.

UNIVERSITY COLLEGE, LONDON.

FACULTY OF MEDICINE.

The Classes re-commence on MAY 1, and are so arranged as to afford a convenient opportunity for Students to commence their Medical Course. Full information may be obtained from the Office of the College, Gower Street, W.C. JOHN WILLIAMS. M.D., Dean. J. M. HORSBURGH, M.A., Secretary.

AND TO PRODUCE THE PHENOMENA OF SOUND. NEW ILLUSTRATED CATALOGUE, Containing Price Lists in French, English, and German. 100 Pages. 132 Engravings. Post Free, 3 Francs. To Scientific Institutions Free.

Paris-27 Quai d'Anjou Paris.

TO SCIENCE LECTURERS.

See Mr. HUGHES'S PATENT COMBINATION OPTICAL LAN. TERN, used by W. LANT CARPENTER, Esq., Prof. FORBES, B. J. MALDEN, Esq. New Oxyhydrogen Microscope. Grand Results. Docwra Triple, Prize Medal, Highest Award. Patent Pamphagos Lantern Science Lecture Sets. Novelties Cheapest and Best. Elaborately Illustrated Catalogue, 300 Pages, 1s.; Postage, 5d. Smaller do., 6d. Pamphlets Free. HUGHES, Specialist, Brewster House, Mortimer Road, Kingsland, N.

SILVERED-GLASS REFLECTING

TELESCOPES.

CALVER'S well-known TELESCOPES received the Highest Award for "Excellence and Improvements" at the International Exhibition, London. Catalogues and Testimonials, 15.-G. CALVER, F.R.A.S., Widford, Chelmsford.