AN ACHROMATIC COMBINATION. COMBINING THE DEFINITION OF A MICROSCOPE WITH THE "If you carry a small Platyscopic Pocket Lens (which every observer of Nature ought to do)."-GRANT ALLEN, in Knowledge. "I have long carried one of these instruments and found it invaluable."-JOHN T. CARRINGTON, Editor of Science Gossip. The Platyscopic Lens is invaluable to botanists, mineralogists, or entomologists, as it focuses about three times as far from the object as the Coddington Lens, and has a field unequalled for flatness, allowing opaque objects to be examined easily. It is made in four degrees of power, magnifying respectively 10, 15, 20, and 30 diams.; the lowest power, having the largest field, is the best adapted for general use. Mounted in Tortoiseshell, magnifying 10, 15, 20, or 30 S. d. In Nickelised German Silver, either power 15 0 ... 17 6 27 6 ILLUSTRATED DESCRIPTION SENT FREE. 32 6 THE STATEMENT THAT SECCOTINE STICKS EVERYTHING may seem to claim too much; but the constantly recurring instances of its successful use in matters beyond ordinary making and mending go far to justify the claim. The British Medical Journal (Jan. 4, 1902) contains an illustrated article on a case of supply of an artificial ear. The writer says, "The application of Seccotine has been found quite sufficient for the necessary adhesion of the internal surface of the artificial auricle to the corresponding parts remaining." At the time of writing this article the artificial ear had been worn by its owner, a boy, for TWO YEARS. A small Sample Tube for trial can be had for nothing and post free on application to Sole ProprietorsM'CAW, STEVENSON & ORR, Ltd., BELFAST, and at 31 & 32 Shoe Lane, Ludgate Circus, London, E.C. SECCOTINE IS ON SALE IN EVERY TOWN IN THE KINGDOM. Dew Point Appar THE POLYMETER. A miniature Meteorological Observatory for Scientific, OUR CATALOGUE (650 pages of Illustrations and Prices) OF EVERY DESCRIPTION OF CHEMICAL & ANALYTICAL APPARATUS. Including Balances, Drying-Ovens, Furnaces, Hot may be had gratis on application by Colleges, Schools A. GALLENKAMP & CO., LTD., 19 & 21 SUN ST., FINSBURY SQ., LONDON, E.C. THE ARISTON" LIQUID AIR AND LIQUID HYDROGEN. FINE ADJUSTMENT (PATENT) FOR MICROSCOPES See Commendatory Notice in NATURE, LISTS POST FREE. JAMES SWIFT & SON, 81 TOTTENHAM COURT ROAD, LONDON. Dr. HAMPSON'S AIR-LIQUEFIER is now made to a standard pattern, and numbers are in use in University Laboratories and elsewhere in various countries. The whole apparatus is neat and compact and its parts very easily moved; the Liquefier, without stand, being a cylinder 17 inches high and 8 inches in diameter. It begins to liquefy air in from 6 to 10 minutes after the admission of air at from 150 to 200 atmospheres pressure, making over a litre of liquid per hour. It requires no auxiliary refrigerant and produces a perfectly clear 1 quid which requires no filtering. The operator has only one gauge to watch and one valve to control. HYDROGEN LIQUEFIER to the designs of Dr. MORRIS W. TRAVERS for use in conjunction with Air-Liquefier. For Prices and Particulars apply to the Sole Makers :BRIN'S OXYGEN COMPANY, LIMITED, WESTMINSTER, LONDON. COLOUR PHOTOGRAPHY. SANGER-SHEPHERD QUICK HANGE, ONE PLATE, LATEST PATTERN OUTFITS. EXCELLENT Photographs in Colour are obtained with our smaller lens filter Outfits, complete from 25/-; but for general work, Landscapes in changing light, Portraiture or Ph tomicrography where rapid exposures in succession are necessary, the Repeating Back with Colour Filters is recommended as the best all round appliance. It may be attached to any, or whole-plate camera or glass plate Kodak, by means of a panel cut to correspond and interchangeable with the ordinary dark slide. This does not in any way interfere with the use of the camera for ordinary work. The three Colour Filters are held in a frame, clipped in front of the double dark slide which carries the two plates, each large enough to record the three negatives side by side, when the slide is pushed past the opening in the outer case. With this Outfit, even a beginner will secure three-colour negatives with the ease and certainty of an ordinary photograph. Repeating Back Attachments, with Filters complete, from 90/Write for new illustrated price list, mentioning NATURE, or call to see transparencies and paper prints by THE SANGER SHEPHERD process. SANGER-SHEPHERD & CO., 5, 6, 7 Gray's Inn Passage, Red Lion Street, Holborn, London. Leach's Lantern Microscope 1800 This Lantern Attachment is by far the most efficient of all the instruments yet introduced for the production of Microscopic objects upon the screen. Mr. Leach's improvements, and the high-class quality of its lenses, combine to give better definition than has hitherto been attained even at the most extravagant prices. It can be attached to any ordinary limelight lantern by screwing it into the flange which carries the usual lantern objective. Any good ordinary objective can be used, but specially selected ones for flatness and largeness of field answer the best. £9: 10 : 0. JAMES WOOLLEY, SONS & CO., Ltd., VICTORIA BRIDGE, MANCHESTER. Chemical and Physical Apparatus of every description. CATALOGUES ON APPLICATION. FORTHCOMING BOOKS In the University Tutorial Series. ARITHMETIC, THE JUNIOR. (Suitable for the ARITHMETIC, CLIVE'S SHILLING. (Suitable for 3s. 6d. BOTANY, ADVANCED. (Suitable for the Second Stage DYNAMICS, THE TUTORIAL. By WM. BR GGS, [In preparation. GEOMETRY, PRELIMINARY. (For the Preliminary Cambridge Locals, and similar Examinations.) By W. P. WORKMAN, M.A., B.Sc. 1. 6d. [In active preparation. GEOMETRY, PRACTICAL PLANE AND SOLID. (Written to meet the Requirements of the First Stage of the New Syllabus (1902-3) of the Board of Education.) By G. F. BURN, A. M. I. Mech. E. 25. [Ready. GRAPHS: The Graphical Representation of Algebraic Functions. Being a Supplement to "The New Matriculation Algebra." By C. H. FRENCH, M. A., and G. OSBORN, M. A. 6d. [Ready. HEAT, HIGHER TEXT-BOOK OF. By R. W. STEWART, D.Sc. Lond. 6s. 6d. [Ready. MAGNETISM AND ELECTRICITY, HIGHER TEXT-BOOK OF. By R. W. STEWART, D.Sc. 6. 6d. [In the press. NAVIGATION, MODERN. (Suitable for Examinations conducted by the Royal Navy, and by the Board of Education in Subjects XX. and XXIB.) By Rev. W. HALL, R.N. 6s. 6d. [In the press. PSYCHOLOGY, THE GROUNDWORK OF. By G. F. STOUT, M.A. Camb. and Oxon., LL. D. Aberdeen. 4s. 6d. [Ready. STATICS, THE TUTORIAL. By WM. BRIGGS, LL. D., M.A., F.C.S., F. R. A. S., and G. H. BRYAN, Sc.D., M. A. F.R.S., Smith's Prizeman, late Fellow of St. Peter's College, Cambridge. Third Edition, Revised and Enlarged. 35. 6d. [Ready. Complete Catalogue, and Lists of Books for LONDON UNIVERSITY and other Examinations London: W. B. CLIVE, University Tutorial Press Warehouse, 157 Drury Lane, W.C. THURSDAY, DECEMBER 3, 1903. book, which is "practical," and occupies 224 pages. This is occupied wholly by constructions, and many of these constructions are to be taken in conjunction with THE REFORMATION OF THE TEACHING OF corresponding theorems, to which the pupil is duly GEOMETRY. Elementary Geometry, Practical and Theoretical. By referred in part iii. of the book, which is "theoretical." It must not be supposed, however, that part ii. is merely constructive-that is, that the pupil is directed to perform certain operations without understanding the reason. The constructions are, almost invariably, accompanied by a justifying proof, and the whole collection seems to be exhaustive. Here the nature of an envelope is also explained, and a few examples of the drawing of envelopes are given. Under the head of constructions we find also the EIGHT years ago the writer of this review, when definitions of the trigonometrical functions, and some publishing a small book on geometry for the use of pupils of eight or nine years of age, was assured by many friends that the attempt to get rid of Euclid's order and language was a hopeless one, and that, even if it were successful, the foundations of all logical thought in England would be destroyed. Against at strong conservatism it seemed vain to point out that the great developments of modern geometry were made by European mathematicians who were not brought up on Euclid. The question had been tackled before, but with no success. When, however, the British Association and the Mathematical Association appointed committees to grapple with the matter in earnest, the victory of reform was assured. The former body thought it wise to lay down generalities, while the latter went into such minute details as to the course to be pursued by teachers, and the propositions which should be included in school instruction, that it has been possible to embody its recommendations in definite systematic treatises, such as the two excellent works the titles of which are quoted above. That some recognised order of deduction must be established is a fact which is forced upon anyone who has to perform the part of an examiner, more especially for the public service, and the fact that there is a close agreement, not only in method, but in order, between the two works before us shows that the difficulty of dethroning Euclid is quite imaginary. Each of these books is a vigorous protest against the extraordinary contention which we have sometimes heard, that "you must make bad figures in geometry so that the logical faculty of the pupil shall receive no assistance from them." Rule, compass, set square, and protractor are now the tools with which the young pupil begins his acquaintance with this subject; and we venture to say that, under the new system, the typical schoolboy will change his attitude of repugnance to "that beastly Euclid "; the subject will actually become popular. in The work of Messrs. Godfrey and Siddons begins with fifty-nine pages of "experimental geometry, which the pupil is taught to draw various figures by the use of scales, compasses, &c. There is no formal list of definitions; the definitions are given as they are required. Messrs. Barnard and Child open with a list of definitions, each of which, however, is illustrated by a good clear figure, and then follows part ii. of the constructions founded thereon, so far as one angle is concerned. There is also a section dealing with the displacement of a lamina in its own plane, and the nature of the instantaneous centre of rotation. It is needless to say that the plotting of figures on squared paper and the measurement of areas thereby occupy a fair space in this section. The principles of folding and superposition, also, are largely employed as a means of proof. There is no doubt that in this work of Messrs. Barnard and Child the teacher will find every requisite for the modern teaching of geometry, including a very large number of illustrative examples. The collection of all construction propositions into one large section by themselves is the main difference between the two works before us. In the work of Messrs. Godfrey and Siddons the constructions appropriate to each branch of the subject form a special section in that branch; thus constructions relating solely to triangles are taken together in the part of the book dealing with congruent triangles, those relating to circles in the part dealing with circles. There is a remarkable similarity of procedure in the theoretical or deductive portions of both works. Each begins with the discussion of angles at a point, then follow the treatment of parallel lines, angles of a triangle and external angles of a polygon, congruent triangles, inequalities (i.e. of sides and angles of a triangle) and parallelograms, closely followed in each work by the discussion of areas. Messrs. Godfrey and Siddons adopt the invariable plan of accompanying each proposition with a large series of examples and applications. Sometimes we come across a well chosen practical example calculated to enlist the interest and sympathy of the young pupil such as the application of a simple case of congruent triangles to the finding of the breadth of a river, of which a figure is given. The work is a charming one, marked by great simplicity. Squared paper and the plotting of coordinates find also ample space in this book. Geometry is supposed to have arisen from the necessities of land-surveyors, but any such mundane connection has been so long severed that we find ourselves astonished when we actually see (p. 180) an irregular figure plotted and its area estimated by a process of give and take and this in the midst of some of Euclid's propositions, too! Truly the times have altered rapidly—a still further proof of which fact is furnished by the liberty which each of these excellent works takes with Euclid's Prop. 19, Bk. vi.-" similar triangles are to one another in the duplicate ratio of their homologous sides" mysterious but high-sounding to countless generations of schoolboys. Here it is, in identical words in both books, "the ratio of the areas of similar triangles, or of two similar polygons, is equal to the ratio of the squares on corresponding sides," brought down to definiteness and intelligibility at last! There are certain time-honoured propositions in the treatment of which teachers will take a special interest, and none more prominent than Euclid's Prop. I of Bk. vi. Messrs. Barnard and Child prove it by assuming that the bases of the triangles are multiples of some common length, while Messrs. Godfrey and Siddons (p. 175) treat it as a mere result of the fact that the area of a triangle is half the product of a base and the corresponding perpendicular-both proofs, of course, resting on the same ultimate assumption. In justification of such proofs it may be said that no useful purpose will be effected by an early discussion of incommensurable quantities. There are many things-such, for example, as the constancy of the product of the radii vectores from a fixed point to a circle, the nature of a tangent as a limiting position of a chord, &c.-in which we have an agreeable and useful variety of treatment in these two works, but the limitation of space renders further reference to them here impossible. THE HE pre ace of this work informs us that its author has endeavoured to conform strictly to the principle laid down by Lord Kelvin, as follows:-" If a probable solution, consistent with the ordinary course of nature, can be found, we must not invoke an abnormal act of Creative Power." Unfortunately the "Semi-Darwinian's" practice is not in accord with his profession. Whenever he meets with a problem in evolution which appears to him inexplicable on the lines of natural selection, so far from seeking for a probable solution, consistent with the ordinary course of nature," he resorts at once to the intervention, by a direct creative act, of "a Being possessing intelligence, intention and power." This is bad science, and we much doubt whether it is good theology. 66 Opinions have differed, and will doubtless for a long time continue to differ, as to the extent of the influence of natural selection as a factor in evolution. Darwin himself, as is well known, thought that its operation might be supplemented by that of the factors adduced by Buffon and Lamarck. Whether in view of the increase of knowledge since Darwin's day, and of the numerous cases of difficulty which have lately been satisfactorily explained on the basis of natural selection, he would have been led to discard those hypotheses that involve the hereditary transmission of acquired characters, it is, of course, impossible to say. But it certainly seems probable to those workers in whom the Darwinian tradition is strongest that their leader, were he living now, would attribute more rather than less importance to his distinctive principle of natural selection. However this may be, the fact remains that if by " Darwinism " be meant the natural selection of "accidental" variations, the doubt as to its claim to be the sole factor in evolution is a doubt that was felt by Darwin himself. Hence we demur to the title of the present work. A matter of greater importance is the author's attempted demonstration of the impossibility of explaining certain phenomena on Darwinian principles. It is true that some of the facts he adduces have been felt as difficulties, but not, as a rule, in the way that he supposes. To answer his objections point by point would be lost labour, for he shows on almost every page that he is unacquainted with the conditions of the problem. His remarks on the subject of vision, of reproduction, of embryology, to take a few instances, are those of a disputant who has entered the lists without the necessary equipment. Argument with such an opponent is unprofitable. As an example of the failure of the "Semi-Darwinian " to master the present-day aspects of the subject, we may take his treatment of the caterpillar and beetle-stabbing instincts of Sphex and some other genera of fossorial Hymenoptera. He quotes Romanes's expression of a desire for further investigation of the facts, but appears to be quite unaware that the need has been to a great extent supplied by the labours of two industrious and accurate naturalists in America, who have put an entirely new complexion on the case as it was known to Darwin. We have no wish to detract from the merits of so zealous and patient an observer as Fabre, to whose writings those who have discussed the habits of Sphex, Ammophila, and their allies have generally been indebted for their facts; but it is impossible to study the recent work on the subject without recognising that Fabre's inferences are sometimes unwarranted. Even before the new facts had been brought forward by G. and E. Peckham, the difficulties of explanation on the lines of natural selection, though great, did not seem insuperable; they may now be said to have disappeared. But it is not only on such points of detail as the foregoing that the author shows his absence of qualification for dealing with the modern phases of the evolutionary problem. To say nothing of other omissions, the whole series of considerations specially associated with the names of Baldwin, Lloyd Morgan and Osborn is entirely ignored by him, nor does he give any sign of being acquainted with recent views on the subject of heredity. In short, as an attack on the adequacy of natural selection, his book, besides being ineffective, is hopelessly belated. Supposing, however, that the author's strictures were well founded; that he had really contrived to point out certain stages in the evolutionary process which are not, and apparently never can be, explained on the basis of natural selection-what then? Surely in accordance with his own canon his next step should be to search for some other natural cause of the phenomena that baffle him. To fly at once to the 6 WATER SUPPLY. Water Supply. A Student's Handbook on the Con- THE HE provision of a pure and ample water supply is constantly growing in importance with the development of sanitary science and the rapid increase of the population in cities and large towns; whilst adequate and unpolluted sources of supply have to be sought at greater distances away, and in a country of limited area, such as England, will before very long become difficult to obtain, yielding sufficient quantities of water to meet the growing requirements of the inhabitants. Accordingly, water supply has within recent years become one of the most universally needed branches of engineering; whereas increasing difficulties are encountered in the execution of the requisite works. The enhanced value and interest thereby conferred on works providing supplies of water, have naturally led to the publication of several books on the subject in the last few years; but the present book differs from its more elaborate and comprehensive predecessors, in dealing with principles rather than with practice, and in being intended as a sort of introduction to those larger books, and for engineering students rather than for engineers. The first introductory chapter gives a rapid sketch, within the limits of six pages, of the various points which have to be taken into consideration in devising a scheme of water supply, from the selection of a source to the delivery of the water to the consumer; and it provides a clear and useful summary of the questions which form the subjects of the succeeding chapters. The second and third chapters deal respectively with the requirements as to the quality and the quantity of water, the former describing the mineral and organic impurities liable to be found in water, the sources from which they are derived, and their relative importance; whilst the latter explains the variation in the daily consumption per head of population in different localities, under different conditions, at different seasons, and according to the amount of waste, also the provision necessary for increase in population, the method of measuring rainfall, the gauging of the discharge of streams and rivers, and the estimation of the available yield from the different sources of supply. In the following chapter, on storage reservoirs, the form and construction of earthen dams, and the various arrangements resorted to for regulating the discharge of the water from the outlet of reservoirs, are the main subjects dealt with; and under the heading "Compensation Water," concluding the chapter, after explaining this important requirement, a description is somewhat irrelevantly added of the earthen embankments of the Staines reservoirs, with which the author is professionally connected, the only definite reference to an executed work given in the book. The next chapter is devoted to the calculations of stability of masonry dams by analytical methods, but a graphical treatment of the statical problems involved would be found both clearer and simpler. An interesting description is given in chapter vi. of the purification of water by the ordinary English system of slow filtration through sand; and a brief reference is made at the end of the chapter to the American system of | rapid filtration by aid of a coagulant, usually aluminium sulphate, introduced into the water. The construction of service reservoirs for providing against fluctuations in the consumption is considered in a short chapter; and it is followed by a fairly complete investigation of the flow of water through pipes, occupying twenty-seven pages. The last three of the eleven chapters in the book, relating to distribution systems, pumping machinery, and requirements in connection with waterworks, together covering less than nine pages, add more to the number of chapters. and the apparent scope of the book than to actual information about waterworks, the last chapter, more particularly, consisting simply of an appeal for the collection of additional and more detailed statistics in regard to rainfall, evaporation, the discharge of rivers. and streams, and other matters pertaining to water supply. The book is illustrated by four folding plates and sixty-six figures in the text, and a short index is added at the end. Though some subjects, such as aqueducts from impounding reservoirs, water meters, and sections of typical masonry dams are not described, and the information about springs and wells is scanty, and the book, therefore, does not provide a complete account of waterworks, it gives a considerable amount of practical information, combined with valuable suggestions for the guidance of waterworks' engineers in several of the chapters. The way, however, in which the book is written renders it more likely to be used for reference than for reading straight through; and, moreover, the number of short paragraphs into which it is broken up, even when treating of a single subject, is calculated to distract the reader. Nevertheless, the engineering student will find a considerable store of useful information and valuable hints dispersed |