5-in. Condensers. RADIUM ROD. This consists of a metal handle with Ebonite Top having a removable Aluminium Cap covering the RADIUM PREPARATION With this all the Physical Properties of Radio-activity can readily be shown. Price £4 15s. in Elegant Case. NEWTON & CO., 3 FLEET ST., LONDON. 14 Commercial St., Leeds. ENGINEERING AND CHEMISTRY. CITY AND GUILDS OF LONDON INSTITUTE. SESSION 1905-1906. The COURSES of INSTRUCTION at the Institute's CENTRAL TECHNICAL COLLEGE (Exhibition Road) are for Students not under 16 years of age; those at the Institute's TECHNICAL COLLEGE, FINSBURY, for Students not under 14 years of age. The Entrance Examinations to both Colleges are held in September. Particulars of the Entrance Examin. ations, Scholarships, Fees, and Courses of Study, may be obtained from the respective Colleges, or from the Head Office of the Institute, Gresham College, Basinghall Street, E.C. CITY AND GUILDS CENTRAL TECHNICAL COLLEGE. NORTHAMPTON INSTITUTE, CLERKENWELL, LONDON, E.C. ENGINEERING DAY COURSES IN MECHANICAL, ELECTRICAL, AND HOROLOGICAL ENGINEERING. FULL DAY COURSES in the THEORY and PRACTICE of the above subjects will commence on MONDAY, OCTOBER 2, 1905. ENTRANCE EXAMINATION on WEDNESDAY and THURSDAY, SEPTEMBER 27 and 28. The Courses for Mechanical and Electrical Engineering include periods spent in Commercial Workshops, and extend over four years. They also prepare for the degree of B.Sc. in Engineering at the University of London. Fees for either of these Courses, £15 or 11 per annum. Three Entrance Scholarships of the value of £52 each, giving free tuition for the full course in Mechanical or Electrical Engineering, will be offered for competition at the Entrance Examination in September next. Conditions can be obtained from the PRINCIPAL. Full particulars as to fees, dates, &c., and all information respecting the work of the Institute, can be obtained at the Institute or on application to SUNDERLAND PUBLIC LIBRARY, MUSEUM, AND ART GALLERY. ASSISTANT CURATOR. Applications are invited for the position of ASSISTANT CURATOR to the above Institution. Applicants must be experienced in Classification, and possess a good general knowledge of practical Museum Work. The gentleman appointed will be expected to give the whole of his time to the duties of the office, and not engage in any outside work. The salary will commence at £91 per annum. Applications, stating qualifications and experience, together with copies of three recent testimonials, which will not be returned, should be marked "Assistant Curator," addressed to THE CHAIRMAN OF THE MUSEUM AND LIBRARY COMMITTEE, and delivered at the Public Library not later than MONDAY, 31st inst. Canvassing Members of the Committee is a disqualification which will be strictly enforced, except in the case of the candidates who will be selected to meet the Committee prior to the appointment. INDIAN FOREST SERVICE. THE SECRETARY OF STATE FOR INDIA IN COUNCIL gives notice that, in view of the late date at which the Regulations for the Appointment of Probationers to the Indian Forest Service were published this year, he has decided to modify them— (a) by extending till Tuesday, August 1, the period within which appli cations will be received; (6) by admitting to the examination candidates who undertake to pass Responsions or its equivalent before October next, failing which their selection would be cancelled; (c) by permitting candidates to offer Zoology at their discretion. Applications for admission to the examination must be made on a printed form to be obtained (with the revised Regulations) from the SECRETARY, Judicial and Public Department, India Office, Whitehall, London, S. W. The age limits are 18 to 21 years on January 1, 1905. Not less than 13 candidates will be selected, if fully qualified. July 5, 1905. A. GODLEY, Under Secretary of State. BIRKBECK COLLEGE. The Council invite applications for the appointment of ASSISTANT LECTURER in MATHEMATICS. Cominencing salary, 175, to dale from September 15 next. Applications, stating age, degrees and qualifications, teaching experi ence, and enclosing testimonials, must reach the PRINCIPAL not later than August 30. Birkbeck College, Breams Buildings, Chancery Lane, E.C. LATYMER UPPER SCHOOL, HAMMERSMITH, W. WANTED, September, ASSISTANT MASTER specially qualified in PHYSICS and GERMAN. Minimum salary first year, £170. Apply COUNTY BOROUGH OF CROYDON. EDUCATION COMMITTEE. The Committee invite applications for the post of PRINCIPAL of the POLYTECHNICS, at a salary of £350 per annum. The gentleman appointed will be required to devote the whole of his time to the duties of his office, and will be responsible for the development and organisation, discipline, and educational efficiency of the instruction given in the Polytechnics. The instruction at these Centres is, for the most part, given in the evening, and in addition to classes in Science, Art, Trade, Con mercial and Domestic Subjects, there are evening courses in Mechanical and Electrical Engineering. The Principal will also be required to superintend any other evening classes established or to be established by the Committee, and to advise and assist the Committee in the co-ordination of all classes of education. Candidates must not be over 45 years of age, and must hold University or other professional qualification. A prospectus of the classes held in the Polytechnics, together with copies of the form of application and statement of duties, may be obtained from the undersigned, to whom applications, accompanied by copies of testimonials of recent date, must be sent not later than September 11, 1905. JAMES SMYTH, Clerk. Education Office, Katharine Street, Croydon, July 20, 1905. To SCIENCE and MATHL. MASTERS.Required (1) Theorl. and Practl. Science, Geography, and usual subjects for Secondary School. Commencing salary, £150. School near London. (2) Physics and Maths. for Navy Pupils. High-class Preparatory School. 100, resident. (3) Maths. and Science for Army pupils. £100, resident. (4) Maths., including modern Geometry. 120. nonres. For particulars of the above and many other vacancies, address GRIFFITHS, SMITH, POWELL AND SMITH, Tutorial Agents, 34 Bedford Street, Strand, London. N.B.-The Portraits of Sir A. Geikie, Lord Lister, Prof. Cannizzaro, Prof. von Kölliker, Prof. S. Newcomb, Sir W. Huggins, Lord Rayleigh, and Prof. Suess belong to a New Series and are Photogravures. Proof impressions of these, printed on India paper, may be had from the Publishers, price 55. each; or the Series of 35 Portraits in a Handsome Portfolio for £9, carriage paid. The Portfolio may be had separately, price 6s. CHEQUES AND MONEY ORDERS PAYABLE TO MACMILLAN & Co., LTD. OFFICE OF "NATURE," ST. MARTIN'S ST., LONDON, W.C. MR. EDWARD ARNOLD'S NEW BOOKS. THE EVOLUTION THEORY. Professor of Zoology in the University of Freiburg. Professor J. ARTHUR THOMSON and MARGARET THOMSON. SPECTATOR.-"These two massive volumes are in themselves a monument of research and speculation that will out-live much of the perennial brass of the nineteenth century." Demy 8vo. By ARTHUR SCHUSTER, Ph.D., Sc.D., F.R.S., Professor of Physics at the University of Manchester. With numerous Diagrams. 15s. net. TIMES.-"We have in Dr. Schuster's book a notab'e addition to the literature of Optical Theory, and one which will prove of value to every student." THE CHEMICAL SYNTHESIS OF VITAL PRODUCTS, And the Inter-Relations between Organic Compounds. By R. MELDOLA, F.R.S., V.P.C.S., F.I.C., &c., Professor of Chemistry in the City and Guilds of London Technical College, Finsbury. Super Royal 8vo. 21s. net. THE BECQUEREL RAYS Fitted with ZEISS LENSES. SIZES-6x9 and 9x12 cm., and 3 in. x 41-in. and 5-in. x 4-in. Also 9x 18 cm. for Stereo and Panorama. SUITABLE FOR PLATES, PACK FILMS, AND ROLL FILMS. Illustrated Catalogue, "Pn," Post Free on application. NATURE says: The firm of Leybold Nachfolger in Cologne has recently issued a very complete and interesting catalogue of physical apparatus and fittings sold by them. The book starts with a history of the instruments made in Cologne during the last century. In its second section we find an account of the construction and fittings of various chemical and physical institutions. After this follows the catalogue proper, filling some 800 large pages, profusely illustrated and admirably arranged. The book will be most useful to the teacher." (No. 1846, Vol. 71.) THE CATALOGUE WILL BE FORWARDED TO SCHOOLS THURSDAY, JULY 27, 1905. THE AGENTS OF EARTH SCULPTURE. Geology-Processes and their Results. By Thomas C. Chamberlin and Rollin D. Salisbury. Pp. xix+ 654- (London: John Murray, 1905.) Price 215. net. IT T is appropriate that this work is written by experienced members of the United States Geological Survey who are likewise heads respectively of the departments of geology and geography in the University of Chicago. The main portion of the volume treats of the earth's physical features and their origin, and thus illustrates the forces and processes which belong to the borderland between past and present in which geologists and geographers are alike concerned. No aspect of geology appeals to a larger circle of interested students and general readers. The preface being dated from the University of Chicago, it may be inferred that the book is published simultaneously in the United States. It is printed in bold type on thick paper, and with such abundant illustrations that it is a veritable picturebook. There are 24 plates and 471 text illustrations; the latter are not listed, however, in the table of contents. In the eyes of a book-lover the appearance of the book is somewhat marred by its being cut down rather too closely; but as the student will pay more attention to the subject-matter he may at once be assured that it is a sound, vigorously written work, abounding in original information and suggestions, and abreast of the ever-expanding knowledge to which American geologists have so largely contributed. Nor is there wanting due acknowledgment of many facts and illustrations drawn from published sources. In their preliminary remarks the authors make a noteworthy use of statistics. Thus we read that "The total mass of the atmosphere is estimated at five quadrillion tons," that "About 1300 quadrillion tons of water lie upon the surface of the solid earth," and that the volume of the stony portion is about 260,000 million cubic miles. These estimates, incomprehensible by themselves, are rendered useful by comparisons, and the relative mass and extent of atmosphere, hydrosphere, and lithosphere are thereby brought clearly before the reader. It is pointed out that the oceanic depressions rather than the continental masses are the master phenomena of the earth's surface, and that if the surface were graded to a common level by cutting away the land and dumping the matter in the abysmal basins, the average plane would lie somewhere near 9000 feet below sea-level. In dealing with the atmosphere as a geological agent, dust and blown sand, wind-ripples and winderosion, the influence of the colour of rocks on their daily range of temperature, the creep of soils and subsoils, and even the effects of lightning receive attention. Rain and river erosion are discussed from hypothetical, and more fully from actual, points of view. Various stages in the history of streams and valleys are illustrated, and their distinguishing features in youth, in mature and in old age are described. It is pointed out that the base-level of erosion and sealevel are by no means synonymous, as rivers often erode below sea-level. The development of rivers. under different structural conditions is explained, and attention is directed even to the possible influence of the rotation of the earth on the erosive action of streams. The beheading of one stream by another is treated as piracy," and both foreign" and domestic piracy are explained, the latter phrase being applied to cutting off an ox-bow in a meandering stream. Other terms of a somewhat homely nature are used, such as "scour and fill," in illustration of the fact that a stream in flood degrades its channel and aggrades (builds up) its plain. 64 66 There is a notable chapter on ground-water, a subject of great scientific interest as well as practical importance. The movements of ground-water include 66 water table," the fluctuations in its upper surface or and those dependent on the outflow of water in springs or on its abstraction by pumping, influenced as the movements also are by geological structure. The work of snow and ice, of continental and an attractive and alpine glaciers, is treated in luminous style. The way of “ getting load," the englacial and superglacial drift, the transfers of load from basal to higher portions of the ice, and the movements accompanied by shearing-planes and thrusts, are duly described. Hanging valleys" receive attention, and it is remarked that those developed by stream-erosion are not common, except in cases of the recession of a waterfall past the mouth of a tributary. The features are characteristic of regions recently glaciated, where, as in the western mountains of North America and elsewhere, a main valley has been deepened by glacial action below the level of tributary streams. The work of the ocean is fully discussed and illustrated. The cutting of cliffs in different materials. the formation of arches, stacks, and beaches, and rillmarks on sands that simulate sea-weeds, and other subjects large and small come under consideration. The later chapters are occupied by "the origin and descent of rocks"; minerals and rocks are described, and some account is given of the new, and by no means popular, American petrological classification and nomenclature. Various structural features, crossbedding, nodules, joints, folds, &c., as well as deformations, volcanic action, and other topics, are illustrated. The geological functions of life are then dealt with. The consumption and restoration of carbon dioxide and the consequent influence on climate are discussed. The agency of organisms in the disintegration of rocks, and the protection they afford against erosion are pointed out. Attention is also directed to the influence of land vegetation on the character of sediments, due in the first place to the decomposition of different rocks and the formation of soils-materials which may be carried out to sea. On the other hand, "if the surface be bare of vegetation, the crystalline rocks are usually disaggregated before they are de |