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support of a healthy community life. Even if the American farmer is indifferent to the appeal for better surroundings as set forth in these pages, many of the problems discussed demand consideration on account of their economic importance. In the matter of roads, for instance, only 8 to 9 per cent. of the total roads of the States have been improved by surfacing with gravel, oyster shells, etc., whilst the remainder are often so despicably bad that the cost of haulage of farm products is three to four times the legitimate amount. The one-street town is passing away, and many of the suggestions advanced by Mr. Waugh as to farm and town planning are well worthy of practical adoption.
TEXT-BOOKS OF PHYSICS.
(1) Cours de Physique. By Prof. E. Rothé. Pp. vi+183. (Paris: Gauthier-Villars et Cie, 1914.) Price 6.50 francs. (2) Traité de Physique. By Prof. O. D. Chwolson. Translated by E. Davaux. Pp. vi+266. (Paris: A Hermann et Fils, 1914.) Price 9 francs.
(3) Preliminary Practical Science. Some Fundamental Principles of Physical Science, with their Practical Applications. By H. Stanley. Pp. viii+128. (London: Methuen and Co., Ltd., n.d.) Price Is. 6d.
(4) Outlines of Applied Physics. By H. Stanley. Pp. viii+227. (London: Mills and Boon, Ltd., 1914.) Price 2s. 6d..
(5) Preliminary Practical Physics. Part ii. Heat. By A. E. Lyster. Pp. vii+73. (Dublin: Educational Co. of Ireland, 1914.) Price 7d. net.
(6) A School Electricity. By C. J. L. Wagstaff. Pp. xi+250. (Cambridge: At the University Press, 1914.) Price 5s. net.
(7) Elementary Geometrical Optics. By A. S. Ramsey. Pp. xi+173. (London: G. Bell and Sons, Ltd., 1914.) Price 6s.
S judged by the size of the first two books of the "Cours de Physique," which Prof. Rothe is writing, the whole work will be of very considerable magnitude. According to the author's foreword, these two books represent the introduction only to the course itself, which is intended for students who have already studied physics, and primarily for those who are proceeding to technical institutes. In several ways this introduction is rather remarkable. The subjects covered in the first book are (i) units, and their transformation from one system to another; (ii) the principle of similitude in physics; and (iii) methods of measuring the fundamental physical quantities, and the errors involved. In the second
book, the statics of fluids and the experimental measurement of densities and pressures are dealt with. There is, perhaps, too little stress laid upon theory, but there can be no doubt that the detailed descriptions of the methods of measurement with great precision, together with the diagrams illustrating these methods, are in every way excellent.
(2) Many physicists regard Prof. Chwolson's treatise on physics as the best in existence—and with justice. Prof. Chwolson has not only given us a most complete and accurate survey of experimental physics in practically all its branches, together with an exhaustive bibliography, but he has also contrived to make his work a critical essay. The translation of this work into French, making it as it will do-available to those students who do not know Russian and read German with difficulty, is a most desirable event. That now published is the tenth part, and contains the chapters on electromagnetic induction, Maxwell's theory, the basis of electronic theory, and the principle of relativity. The translation has the advantage of having been revised by the author himself, who has, at the same time, considerably augmented the edition. The chapters on the theories of electrons and relativity have, consequently, an added interest, and it will be found that they give a very comprehensive survey of these subjects which are at present so much under discussion.
(3) This little volume adds another to the already large number of similar books which have been published within recent years, and follows much the same lines of treatment. A considerable number of simple physical experiments are described, principally in mechanics, heat and light, those in electricity and magnetism numbering only half-a-dozen. Each exercise combines a simple statement of the theory of the experiment and a description of the method of procedure. In some of them, however, the results obtained would not be what the student is led to expect. For example, in the experiment on the spectrum, no lens is used to focus the light on the screen, and we are told incidentally that the spectrum consists of seven colours. A refreshing feature of the book, however, consists of some excellent notes on experimental work which, if all students would follow, would bring about a great improvement in their practical records.
(4) In the main, this book is a series of examples in theoretical physics, for not only are there numerous numerical exercises at the end of each chapter, but more than four hundred of a miscellaneous character at the end of the book. The work, as the author himself points out, is
in no way descriptive, and therefore could not serve as a text-book. Indeed, it seems rather to partake of the "cramming" nature, and would tend to make physics appear to consist of a series of mathematical formulæ. Still, provided that it does not lead students to neglect the experimental side of physics, the book will probably be found quite useful.
(5) This is a little paper-covered pamphlet containing descriptions of some forty simple experiments in heat, and, although small, is well printed and arranged. The diagrams all represent sections of the apparatus, and are free from elaborate details. This is a good feature, for, as the author points out, it will encourage the reader to do the same in his practical records, instead of wasting time over sketching the exact apparatus a thing which but few students can do well.
(6) It is not often that there appears a physical text-book so generally good as this one of Mr. Wagstaff. It is the outcome of the author having been persuaded to publish a book comprising the notes of his lectures at Oundle School, and he is to be congratulated on the result. Not only is the treatment obviously based upon experience in teaching the subject, but the descriptive work and the methods of explaining those parts of the theory which present difficulties to the average student have an originality which is very refreshing. Besides this, all the diagrams and plates are excellent, and these features, together with the good printing of the text, give the book a general appearance which is very pleasing. One or two criticisms may be made. These, however, detract but little from the value of the book. The first is with reference to the definition of the ampere in terms of silver deposited during electrolysis. One knows, of course, that it is so defined by law, but it cannot be clear to a student why the special amount, o'001118 gram per second, is chosen. In fact, we disagree entirely with the position which the author advocates in his preface, viz., that it is desirable to begin teaching current electricity using direct reading instruments such as ammeters, instead of by means of the tangent galvanometer, which, besides having a mode of action which is simpler than that of an ammeter, serves also to measure the current absolutely.
In the second place, the study of electrostatics and magnetism ought to be taken earlier than it is in this book. The book opens with a very short chapter on magnetism, then proceeds with current electricity, and the treatment proper of magnetism and statical electricity is not reached until half-way through. It would, however, be possible
for these chapters to be read first, and the objection would thereby be partially removed. In any case, it is not of great importance, and the book is to be thoroughly recommended.
(7) This book, also, is well produced, and deals with a subject somewhat neglected. Although the treatment is not advanced, it comprises a wide field, including the important subjects of achromatism, thick lenses, and optical instruments. There are frequent examples which will, no doubt, be useful for training the students. It is quite certain that there has been for some time an opening for a book of this kind, and the present volume is well fitted to supply the demand which exists. In fact, students of the subject of light would be well advised to read this volume in conjunction with their text-books of physical optics; and those who intend becoming optical instrument makers would benefit greatly by studying it.
Edema and Nephritis: a Critical, Experimental, and Clinical Study of the Physiology and Pathology of Water Absorption in the Living Organism. By Prof. M. H. Fischer. Second edition. Pp. x+695. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1915.) Price 215. net.
THIS is the second edition of a work which has already attracted some attention in the physiological world. The author's main theme is that dropsy is not due to disorders of the circulation, or to changes in osmotic processes, but is wholly produced by the tissues themselves sucking up water from the blood, and that increase in acidity of the tissues is the sole factor in their being able to attract more water into their colloid structure. The main experiments upon which this theory depends were performed by placing dead frogs' legs and pieces of gelatin in fluids of different composition and reaction. Even the swelling which occurs in a limb when reflux of blood from it is prevented theory. Addition of such salts as sodium chloride by occluding the veins is explained on the acid to the experimental fluid lessens the amount of swelling; yet it is well known that excess of such salts favours dropsy during life. This is ingeniously explained by saying that the excess of salt lessens vital oxidative processes, and this leads to formation of acid, and therefore indirectly œdema. The only piece of evidence advanced in favour of this view is that rabbits on an excessive salt diet become cyanotic; an impartial observer might quite reasonably argue that cyanosis may be the result of the dropsy.
Prof. Fischer argues that disturbances of the circulation cannot be the cause of dropsy because in his dead frogs or strips of gelatin, no circulation was going on at all, and yet they became dropsical. Acidity may be, and probably is, one cause in oedema-production; but this is a
THE facts that this is a fourth edition, and that the author has been before the world for more than fifty years as a student of the subject on which he writes, are sufficient reasons for welcoming it with respect. But the volume itself fully justifies its existence, and it is difficult, if not impossible, to suggest any change in it that would better fit it to serve the purpose for which it was originally issued. The temptation to use a material that facilitates or immediately improves one's work without due regard to its lasting qualities is always very strong, and especially is this the case with those who are so absorbed in the study and practice of pictorial art, that the scientific aspect of their work becomes distasteful to them. But it is not right to accept ignorantly the opinion of the salesman, however honest he may be, or to trust to a few superficial experiments made by one's self or one's friends. The author deals with painting grounds, vehicles, varnishes, pigments, methods, and results, giving just such details concerning them as the artist wishes, or ought to wish, to know.
The previous edition of the treatise was translated into German and edited by Prof. Ostwald, who added a few paragraphs. The author has incorporated the substance of these in the present edition, definitely indicating such paragraphs, and adding to their value by comments of his
He gives, in short, the results of probably all those who are known to have systematically tested pigments for permanency, and usefully, and we think fairly, criticises the methods and results of these investigators. The preservation and restoration of pictures receive due attention, and throughout the volume the style of the author is such that a previous acquaintance with scientific principles and nomenclature is not necessary for the understanding of it.
xii + 199.
Machine-shop Practice. By W. J. Kaup. Pp. Second edition. (New York: John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1914.) Price 5s. 6d. net. In this little book will be found descriptions of the hand- and machine-tools employed in an up-todate workshop, together with clear instructions for their use. The author has desired to lead the pupil in the shop to think, and not merely to do. For this reason the why of each step or operation is emphasised as much as the how. The function of college workshops is to familiarise students with the working properties of the materials employed and with the tools in general use. Such information cannot be adequately obtained from any book, but a book may be very useful for the purpose of supplementing
the verbal explanations of the instructor. not easy to make other than mental notes in the course of workshop practice, and it is often inconvenient to pull a machine, or part of a machine, to pieces for the purpose of explanation.
The book before us will be found to be very helpful in such matters. Probably the most noteworthy feature in it is the clearness of the illustrations. Where most books of the kind contain merely half-tone illustrations of machines (generally from makers' catalogues), the author has given perspective line drawings, and has named the parts clearly on the drawings. These drawings will be found to be of much value, even when the machine installed in the students' workshop differs in detail from that in the book. Nomenclature is not so serious a barrier in this volume as in some American books. We can heartily commend this book to workshop instructors.
LETTERS TO THE EDITOR.
[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]
The Age of the Earth.
WHILE reading through Dr. F. A. Lindemann's defence of Lord Kelvin's estimate of the age of the earth, I was reminded that in spite of the sympathetic spirit in which he always entered into any discussion, he would never allow the least doubt to be thrown on the correctness of his estimate of the earth's age. Yet it is open to several objections: he assumed that the solidified crust, as it was being formed, would sink toward the centre of the earth until it was solid throughout, whereas there can be no doubt about its core being so heavy that the crust material could not
possibly sink. He also assumed a diminishing rate of cooling, whereas the greater portion of the earth's surface is covered by water the bottom temperature of which must have been practically constant for millions of years. He also cuts down the temperature in the earth's centre from 410,000° F., which it would be according to his assumption, to 7000° F.; whereby the available heat is reduced enormously. However, if radio-active processes can supply the earth's radiation losses there is no need to deal with the older question.
I notice that Dr. F. A. Lindemann draws the conclusion that the sun's radiation just compensates the amount lost by the earth, but this is not correct. The earth's loss is estimated from the known temperature gradient in the earth's crust; it is a net loss over and above any possible interchange of heat with the sun. Then, also, Dr. Lindemann limits the earth's age by the sun's age, but amongst the several possible sources of its heat supply he does not even mention the heat-producing power of a meteoric bombardment. Yet, as I have shown in my work, "Unity in Nature," in the chapter on matter (pp. 85-92), it is not at all unlikely in comparatively time the sun may have passed through a large cloud of heavy meteoric matter. One effect of a comparatively slight addition of heavy meteoric matter would have been to increase its density from, say, 100 to 1.38, and the other effect would have been to raise the sun's surface to such a high temperature that it would have evaporated and formed an atmosphere
extending perhaps beyond the orbits of the asteroids. In fact, the difference in the densities of the inner and outer planets and the sun, and the fact that practically all rotations and revolutions are in the same sense, suggest that our solar system once consisted of a sun and the outer planets, all having a very low density, and that on passing through a cloud of heavy meteoric matter, the density of the sun was slightly increased, and the inner heavy planets created; but it is impossible here to go into the details of these interesting questions.
As regards the nearer evidence of the earth's age to be sought for in the sedimentary rocks, no notice seems to have been taken either of the time required for the innumerable raisings and lowerings of level which certainly occurred during the coal periods or of the time which it must have taken to tilt horizontal strata through 90° and more. Thus Japan is being tilted at the rate of about 0.5 per century, and if this tilting rate were steadily maintained in one locality, which is highly improbable, the Japanese strata would
stand on end like our Cambrian strata in about forty million years' time. Yet a few such tiltings were completed before some of our oldest strata were formed and overthrusts suggest a still greater antiquity for the age of sedimentary rocks. C. E. STROMEYER.
"Lancefield," West Didsbury, April 26.
Man's True Thermal Environment. IN connection with Prof. Leonard Hill's very interesting and instructive article on "Healthy Atmospheres (NATURE, April 22), perhaps I may be allowed to direct attention to a paper which I contributed to the Journal of the Scottish Meteorological Society for 1912, entitled "On Atmospheric Cooling and its Measurement: An Experimental Investigation." In that paper will be found a description of an instrument termed a psuchrainometer (vxpaivw= I become cold; and μerpov a measure) which traces on a moving paper strip, a continuous record of the amount of electrical heating needed to maintain at blood heat a body freely exposed to the atmosphere. This seems to serve much the same purpose as Prof. Hill's caleometer. In the same paper I also gave a table of preliminary numerical results obtained by its use in conjunction with an anemometer and selfrecording thermometer, and from these data deduced an empirical formula giving the rate of cooling (4) as a function of temperature and wind velocity.
The question as to whether could always be thus expressed as a function of already existing meteorological data can only be settled by a long continued series of observations with appropriate instruments, in the construction of which I have been engaged for some time. If can be so expressed, then evidently there would be no need for a widespread installation of special apparatus for its measurements. If, however, this hope be disappointed, a new apparatus must be placed in the hands of meteorologists, and the simpler this is the better. I have now constructed a simple psuchrainometer, consisting essentially of a thermometer furnished with a small heater through which a constant current is always passing. This may be termed a "constant energy" psuchrainometer, and I propose to calibrate it against the necessarily more complicated form of constant temperature psuchrainometer, different patterns of which are described both in Prof. Hill's article and in my paper. JAMES ROBERT MILNE. Physical Laboratory, Edinburgh University, April 30.
THE AUSTRALIAN ANTARCTIC
HE most vexed question in antarctic geography has been the nature of the region west of South Victoria Land. D'Urville and Wilkes, who explored that region in 1838 and 1839, reported land in so many localities that it has been generally believed that their tracks skirted a continuous ice-covered and ice-barred land. Ross, however, sailed across the site of explorers have had the same experience. some of the land reported by Wilkes, and later The
view has therefore often been held that this part of Antarctica consists of an archipelago. The first material step toward the solution of this problem was the sledge journey of David, Mawson, and Mackay during Shackleton's expedition. Their journey afforded strong evidence in favour of the continuity of the land; but this land might end far south of Wilkes's track and be separated from it by a fringe of islands. This question has been finally settled by the Australian expedition of 1911 to 1914 under Sir Douglas Mawson. The narrative of its experiences with some indications of its scientific results are given in two massive and superbly illustrated volumes.
The expedition sailed in the Aurora under the skilful command of Capt. Davis, whose soundings between Australia and the opposite coast of Antarctica are themselves of the highest geographical importance. Two bases were established in Antarctica, the main base in Adelie Land (about 142°40' E.), and a western base under Wild in Queen Mary Land (95° E.); at each of these stations elaborate observations were taken, and the expedition established on Macquarrie Island a wireless station, which should be permanently maintained in the interests of Australian meteorology. From each of the bases extensive sledging expeditions were made to explore the surrounding areas. Wild sledged 4° eastward along the northern coast to Queen Mary Land in the hope of reaching Knox Land. A second party under Dr. S. E. Jones travelled westward to the Gaussberg, and thus reached the field of work of the German Antarctic Expedition under Drygalski. From the main base in Adelie Land one sledging party went eastward to Deakin Bay; a second under Bage nearly reached the Magnetic Pole; a western party sledged 41° along the coast which had been seen by D'Urville. A sledge journey eastward over the ice-covered plateau led to one of the most tragic of Antarctic adventures, for Mertz and Ninnis perished on the journey, and only the lucky finding of a food depôt enabled Mawson to crawl back to his base.
The journey toward the South Magnetic Pole under Dr. Bage was one of the most arduous and successful of the sledging expeditions. The party reached lat. 70°36'5" S. and 148°10' E., where the magnet had a dip of 89°43' or only 16
1 "The Home of the Blizzard. Being the Story of the Australasian Antarctic Expedition, 1911-14." By Sir Douglas Mawson. Vol. i. Pp. xxx+349. Vol. ii. Pp. xiii+338. (London: W. Heinemann, 1915.) Price 365. net two volumes.
min. from the vertical. This locality was 175 miles from the point reached by David's party in 1909, so the two journeys gave a nearly full section across Antarctica from South Victoria Land to Wilkes Land.
These great sledge journeys, combined with Capt. Davis's soundings along the coast, have proved the existence of land all along this part of Antarctica, though somewhat south of the positions where it was reported by Wilkes. Thus the Aurora sailed in clear weather over the site of the land marked by Wilkes to the east of his Cape Carr. Nevertheless, the result of the expedition is to confirm the general belief that from Cape
or land extends in some places north of the circle.
The greatest trial of the expedition was the terrific violence of the wind. Gusts of wind are recorded with a velocity of two hundred miles per hour. The rate of 180 miles per hour is said (vol. i., p. 168) to have been common. The average velocities recorded for whole days are unprecedented. Thus on May 15 the mean for the whole twenty-four hours is given as ninety miles per hour. On May 18, a year later, it was 937 miles. The average for May was 60'7 miles per hour. The most appalling testimony to the wind strength is the record that the average speed for
FIG. 1.-The Aurora lying at anchor, Commonwealth Bay. In the distance the ice slopes of the mainland are visible rising to a height of 2000 feet. In the foreground is a striking formation originating by the freezing of spray dashed up by the hurricane wind. From Sir Douglas Mawson's "The Home of the Blizzard." (W. Heinemann.)
Adare, for more than 80° westward, is one continuous ice-capped land, which forms the northern coast of Antarctica. Mawson attaches the name of the American explorer to a small part of this area, but the name of Wilkes Land appears too firmly established for the whole of it to be easily displaced. The discovery by the expedition of Queen Mary Land in the west, the long line of land to the west of Adelie Land, and of King George V. Land on the east has definitely established the northern coast of Antarctica in this district as approximately along the line of the antarctic circle. There are indications, however, from the charts that either shallow water
the whole year was fifty miles per hour (vol. ii., p. 157). Both volumes contain repeated references to hardships due to these hurricanes, and the prevalence of winds blowing at 100 miles per hour with a temperature of 28° F. (vol. i., p. 134) justifies Sir Douglas Mawson's lament that owing to "the rushing might of these eternal blizzards" Wilkes Land is "an accursed country (p. 134). The wind records were apparently mainly made by a Robinson anemometer, which we are told was the greatest source of worry; and as meteorological authorities have issued frequent warnings of the untrustworthiness of anemometers, opinion as to the exact value of the