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The idea is Mr. Whittaker's treatment is essentially mathe


infinite distance in all directions, and gradually in- certain to be valid in the case of the conservative creasing in intensity as they approach the molecule. than in that of the dissipative system-would then We do not think such cases exist, but we did not give a different form for the radiation pressureexpect to discover radium a few years ago.

apparently f= (log + constant)--and this result would Let us now see how Mr. Jeans attempts to deal have to be admitted. On the whole it appears more with the difficulties here suggested. In the first likely that while distributions satisfying Maxwell's seven chapters he follows fairly closely on conventional law of equipartition are always theoretically possible. lines, and deduces the Boltzmann-Maxwell law of dis- other distributions may exist, and may, indeed. tribution, the minimum theorem, the law of partition represent a normal and persistent state of affairs eren of energy, and the isothermal equations according to in conservative systems. the Boyle-Mariotte and van der Waals's laws. In It is remarkable that physicists strain at gnats chapter viii. the author throws over the principle of when put down to study kinetic theory or thermoconservation of energy and assumes that his gas is a dynamics, and yet they swallow camels with comdissipative system in which loss of energy occurs by placency when they read the subject of Mr. Whittaker's radiation. On this hypothesis he finds that when the book, Analytical Dynamics. Some writers even rate of dissipation has become very slow probability go so far as to introduce pages and pages of the considerations indicate tendency to

most unreal dynamical problems into what they call definite statistical specification different from that treatises on physics. given by the ordinary theory. It further appears "The soluble problems of particle dynamics " that such a gas has one principal and a number mostly represent things which have no existence. It of subsidiary temperatures, a notion which we be- | is impossible for a particle to move on a smooth lieve has been previously advanced. In chapters curve or surface because, in the first place, there is ix. and x. Mr. Jeans considers applications of the no such thing as a particle, and in the second place theory of a non-conservative gas, particularly in con- there is no such thing as smooth curve or surface. nection with rates of dissipation of energy, and ratios What constitutes the chief interest of “ Analytical of specific heats.

Dynamics" is the possibility of forming clear mental We thus have a definite attempt to break away from pictures of its results by imagining bodies capable of traditional methods and boldly introduce the notion of performing the motions discussed. dissipation into the kinetic theory. certainly an excellent one. Whether it is free from matical and advanced in character. He opens with objection is a matter which cannot be answered as sections on the displacements of rigid bodies in which the mere result of a critical examination. Often Klein's parameters and Halphen's theorems objections to theories strike the mind of a reader quite composition of screws figure near the commencement. unexpectedly.

In his chapter on equations of motion physicoIn the remaining chapters Mr. Jeans deals with philosophical discursions on force and mass are re“ free path phenomena " such as diffusion, conduction duced to a minimum. This is as it should be, for there of heat, viscosity, and the escape

of gases from are plenty of people who can write about such matters, planetary atmospheres. In this work he is more on but few whose knowledge extends to the more the ordinary lines. We notice as an important important theorems which follow later. The feature the sections dealing with encounters according Lagrangian equations are reached by $ 26, which is to the law of the inverse fifth power. This series of preceded by a definition of holonomic systems. This chapters is of considerable use in affording easy access distinction might with advantage be put into treatises to investigations contained in a much longer form in in physics, for at present students of that subject are the original papers of Boltzmann and other writers. apt to assume that Lagrange's equations in their

Turning back to the chapter on equipartition of ordinary form are universally applicable, which is far energy, we are led to the following inference :- from true. Passing on to chapter V., which deals, Mr. Jeans leaves it an open question whether the inter alia, with moments of inertia, our old friend the conventional law of distribution with its attendant “principle of parallel axes” is treated generally for consequences of equipartition may represent the a quadratic function of coordinates, velocities and ultimate state of a gas, but concludes that in actual accelerations, readers being doubtless assumed to gases such as we see around us where dissipation of know the proof for simple cases. Chapter vii. deals energy occurs a different distribution holds good. with the general theory of vibrations, and the next

The second conclusion seems plausible. But the chapter with non-holonomic and dissipative systems, assumption that equipartition of energy holds even in the first of these two chapters consisting mainly of a conservative system presents difficulties in connec- theory, and the second mainly of examples. The tion with Stefan's law of radiation in a black cavity. most important chapters are those which follow, deal. According to that law the energy of the ether should | ing with the principles of Hamilton and Gauss, the vary as the fourth power of that of the molecules. integral invariants of the Hamiltonian system, and the It might be said that in the “conservative system” representation of a dynamical system of equations by Stefan's law would not necessarily hold good, and means of contact transformations. that there would be no objection to assuming the Mr. Whittaker some time ago presented a energy of the ether to be then directly proportional valuable report to the British Association on the to that of the molecules, or to the temperature. But problem of three bodies, and he tells us that between the usual thermodynamic investigation--which is more 1750 and 1904 more than eight hundred memoirs were

vestigation. Several other interesting chapters follow. This isso. The author, now professor of geography

published on this problem. Even at the Heidelberg

REIN'S JAPAN." congress last August further additions were made to

By J. J. Rein. this literature. In his chapter on the subject, which Japan nach Reisen und Studien.

Vol. i. Natur und Volk des Mikadoreiches. Second is very brief, he discusses the reduction of the equations to a system of the sixth order, thus affording a

edition. Pp. xv+749. (Leipzig: Wilhelm Engeluseful insight into the main features of this difficult in

mann, 1905.) Price 24s. net, paper; 26s. net, cloth.

CHIS the second of It will thus be seen that Mr. Whittaker's treatise collects into book form the outlines of a long in the University of Bonn, was, in 1874, commissioned series of researches for which hitherto it has been by the Prussian Ministry of Commerce to go to Japan necessary to consult English, French, German, and for the purpose of studying and giving an account Italian transactions. In recent years

Italy has both of the trade of Japan and the special branches played no small part in the development of dynamics, of industry there carried on to so high a degree of as may be seen by the number of papers by Levi perfection. The writer of this notice had the pleasure Civita and other writers which have from time to of making the acquaintance of Dr. Rein while in time appeared in the Atti dei Lincei, dealing with Japan, and can testify to the German thoroughness integrals of the equations of motion of holonomic with which Dr. Rein carried out the work for which systems, particular cases of the problem of three bodies, he was commissioned. The results of that work were and allied questions.

two volumes which, from the point of view of the The book is thus written mainly for the advanced author, have been looked upon as the most scientific mathematician. But an interesting feature is the and complete of their kind. Some years after their large number of examples both in the text and appearance in Germany translations were published at the end of the chapters. Of these a good in England (Hodder and Stoughton), but both the many really contain the substance of minor papers German and English editions have for some time been that have been published abroad. Others are fol- out of print, and the author has done well to bring lowed by the reference “ Coll. Exam.,” and while out a new edition, brought up to date in matters both it may be taken for granted that Mr. Whittaker of history and science. For students of Japan it is has made a judicious sélection, some of the ques

almost unnecessary to review the work of Dr. Rein, as tions bearing these references may give foreign it has long had an assured position. mathematicians a little insight into the unpalatable

The opinion of competent authorities was reflected nuts which Cambridge students are expected to waste

by Prof. Chamberlain more than fifteen years ago, time in trying to crack for examination purposes.

when, in an edition of his well known book Things The antics of insects crawling on epicycloids, or the Japanese,” he said :vagaries of particles moving along the intersections " At the risk of offending innumerable authors, we of ellipsoids with hyperboloids of one sheet, are of no

to pick out the following works as scientific interest, and the time spent in “ getting out” probably the best in a general way that are problems of this character might better be employed cessible to English readers : (1) Dr. Rein's ‘ Japan,' in learning something useful. Moreover, Cambridge with its sequel “ The Industries of Japan.'" college examiners have a habit of endowing bodies person wishing to study Japan seriously can diswith the most inconsistent properties in the matter of pense with these admirable volumes.

Of the two, perfect roughness and perfect smoothness. A per

that on the “ Industries" is the better; agriculture, fectly rough body placed on a perfectly smooth surface cattle-raising, forestry, mines, lacquer-work, metalforms as interesting a subject for speculation as the work, commerce, &c., everything, in fact, has been well-known irresistible body meeting the impenetrable studied with a truly German patience, and is set obstacle. What the average college don forgets is forth with a truly German thoroughness. The that roughness or smoothness are matters which other volume is occupied with the physiography of concern two surfaces, not one body.

the country, that is, its geography, fauna, flora, &c., In our opinion a great deal of the artificiality of with an account of the people, both historical and the more elementary parts of dynamics might be ethnographical, and with the topography of the removed by the more frequent introduction of simple various provinces. problems in resisted motion. There are plenty of easy It is this latter volume which is at present beones to be found which would be more helpful to the fore us, and although it may not be so interesting, beginner than problems about ellipsoids rolling on from the practical point of view, as its sequel, it perfectly smooth surfaces formed by the revolution of is more valuable from a scientific and historical cissoids or witches about their axes. Those who have point of view. The book is essentially the same the ability to do more difficult work should pass on as the first edition, but the author has had the to the advanced parts of a book like Mr. Whittaker's assistance of many friends in Japan in bringing it up and learn what foreign mathematicians have been to date, both from a scientific and a historical point doing; this is much more useful.

of view. It is, however, unnecessary to enter into a It remains to add that the books are neatly bound; detailed account or criticism of its contents. the printing and paper are somewhat unned

necessarily The first part of the book is a very complete and luxurious in quality, and-most important of all, the interesting account of the physical geography of Cambridge printers have not forgotten to cut the pages | Japan; in fact, it is the only systematic account which with their guillotine.

G. H. BRYIN. has been published in a European language. When




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Dr. Rein was in Japan he had, for the most part, to

MAKING A PASTURE. depend on himself for the collection of information

The Agricultural Changes required by these Times, on this part of his subject; but in the interval many and Laying down Land to Grass. By R. H. Elliot. ardent students of science have been trained in Japan,

Third edition. Pp. xxiii + 197. (Kelso : Rutherand they have collaborated with him in bringing the ford, 1905.) matter up to date, so we have very valuable chapters


R. ELLIOT and “ Elliot's system " and “ Elliot's on the geological formation of the country, its physio

mixtures" have been not a little before the graphy, hydrography, climate, flora and fauna; while agricultural public during the last ten years or so, very complete lists of books and papers dealing with but we have not before had the opportunity of readthe various departments of the subjects are given ing at length a full account of “the system " as set which will be useful to those who wish to study them

out by the author. thoroughly.

Indeed, we doubt if we should have been very much The part relating to the history of the country has

wiser now, so formless and discursive is the book, had had a section added to it dealing more fully with the not the publishers been kind enough to provide a events which have occurred during the past quarter synopsis for the guidance of the reviewer. of a century, and gives a very good outline of the

To put the matter briefly, Mr. Elliot farms some poor developments which have taken place. It deals, how- high-lying land in the neighbourhood of Kelso, and ever, only with what may be called the natural history has found it profitable to adopt a system of laying it or facts of the subjects involved, and does not attempt down to grass for periods of four to six years, after to explain the natural philosophy or dynamics. No which it will carry two crops of turnips and two ol doubt the author would say that that was beyond the cereals, in the last of which it is laid down again to scope of his work; but it is possible to make descrip-grass for another period. The essence of the system tions much more interesting and intelligent when the is that with the usual grass seeds, or rather with a forces at work are at least indicated, and the direc- grass mixture containing a large proportion of cockstions and amounts of their resultants explained. The foot and the coarse fescues instead of rye grass, a full discussion of this, however, would take us into considerable

of chicory, burnet, sheep's details of historical methods about which there is still parsley, kidney vetch, and other tap-rooted plants are considerable difference of opinion.

sown, although some of these, like the burnet and the Under anthropology and ethnology a considerable chicory, are regarded as undesirable weeds in many amount of new matter has been introduced, in which parts of the country. Mr. Elliot claims that the derp are given the results of recent investigations and roots of these plants, by opening up and, on their speculations. An interesting sketch is given of the decay, aërating the subsoil, act as the most efficient Japanese language and literature and of the manners

agents of cultivation and bring about a great amelioraand customs of the Japanese. A short account is tion in the texture of the soil. Further, he obtains a given of the Japanese calendar and of the national good turf quickly and at little cost, so that when the festivals. The part dealing with the religious con- land comes under the plough again he can grow four ditions of Japan is too short to allow justice to be done crops on the accumulated fertility without the use of to it, and it does not give an adequate account of

any manure. recent developments. The present war with Russia It will be seen that the one point which can in any has been a revelation of the “soul of the people," a way be held to distinguish Mr. Elliot's from other full explanation of which would require a book for systems of temporary pastures is the use of chicory, itself. Still, Dr. Rein might have tried to bring this burnet, and similar plants in the grass mixtures. It section up to date as well as the others. Its full is probably a sound idea to introduce these deepcomprehension, however, requires something more rooting plants, though we should infinitely prefer the than what is usually called a scientific mind, and equally deep-rooting but far more valuable sainfoin and comparatively few men of science seem capable of lucerne anywhere south of the Trent, yet it leaves us entering on it with understanding. They for the wondering what all the coil is about. What is there most part are content to look at a people from the so novel or so fundamental about the scheme that the outside, forgetting the fact that the most powerful Board of Agriculture should have been expected to factors in the evolution of a nation are intellectual take up Mr. Elliot's 1250 acres and by preaching of and spiritual.


revolutionise British agriculture? Mr. The concluding part of the book deals with the Elliot's system appears to have succeeded on his own topography of the country, and is a valuable con- somewhat special soil and climate, but there is little tribution to the subject. Some useful maps are in- reason to suppose it would be equally suitable to the cluded in the book, and a very complete table of con- bulk of our farming land. Indeed, we have only tents renders the various subjects very accessible. Mr. Elliot's opinion that it has succeeded in his own We venture to hope that a new edition of the second case, for though he writes of the experiments on the volume on the “ Industries of Japan” will soon be Clifton on Bowmont farm, of experiments in any rigid forthcoming, for, notwithstanding all the changes

we see no trace. We never read of comparative which have taken place, the industrial Japan depicted results when one part of a field was sown with Elliot's by Prof. Rein still, to a very large extent, remains, mixtures, the other with an ordinary seedsman's preand only from it can the real Japan be known. scription, nor have we any balance sheet setting out!

HENRY DYER. the financial returns from two fields, farmed one on






Mr. Elliot's system, the other in the fashion followed tops, culminates in some great manufacturing city by any reasonable farmer in the district. In fact, the that darkens the heavens with its smoke. It is doubtbook proves nothing more than that Mr. Elliot, by ful how far this method can afford definitely practical using good seed and looking carefully after his grass help in solving the problems of modern industrial land, has improved his farm in his own opinion and society. Still, the historical method is capable of in that of various of his visitors; otherwise the book is a imparting an interest to a science which to not a few farrago of irresponsible talk, of hard words for agri- men is dismal, and certainly anything that can make cultural chemists and science generally, of diatribes our great cities interesting is to be welcomed. Dr. against the Board of Agriculture and everyone else E. Westermarck investigates the position of woman who does not see eye to eye with Mr. Elliot; it bears in early civilisation, showing that she was by no every mark, in fact, of the work of the man with one means, as a rule, a slave and a nonentity, but he idea.

owns that “ the condition of women or their relative independence is by no means a safe gauge of the

culture of a nation.” Mr. P. H. Mann follows with SOCIOLOGY.

a paper on “Life in an Agricultural Village in Sociological Papers Published for the Sociological England,” an investigation of the economic condition Society. Pp. xviii + 292. (London: Macmillan and

of the inhabitants. He follows the method of Mr. Co., Ltd., 1905.) Price ios, 6d.

Charles Booth and Mr. Rowntree in the study of

city populations. Prof. Durkheim and Mr. Branford THE HESE papers, the Transactions of the Sociological discuss the relation of sociology to the social sciences

Society, make known to the world what work and to philosophy. Prof. Durkheim contends that the society has done during the first year of its

sociology is not mere organisation of existence, and explain the aim and scope of the work specialist sciences, but that it is capable of remodelling it hopes to do in the future.

them. Historians, for instance, and political The first paper recounts the history of the word economists have already had “ reorient their sociology. After that we get to the fundamental

studies.” question of eugenics, the science which deals with

In conclusion, we must congratulate the Sociological all the influences that improve the inborn qualities of Society on its first year's work. Beyond the work the race; also with those that develop them to the which can be definitely gauged there has been the utmost advantage." Mr. Francis Galton, the author bringing together of men who hold very different of this paper, would have the principles of eugenics views, and of men who are attacking the same great “introduced into the national conscience, like a new

problem from different sides.

F. W. H. religion," that so a fine race may be bred. The discussion that followed was very interesting. The view held by most medical men who have reached

OUR BOOK SHELF. middle age was put without any qualification, the view that we cannot attempt to deal with “a mass of

First Report of the Wellcome Research Laboratories

at the Gordon Memorial College, Khartoum. By scientific questions affecting heredity," but that we

the Director, Andrew Balfour, M.D., B.Sc., &c. must concentrate our attention on more practical (Khartoum : Department of Education, Sudan questions, such the feeding of infants. Mr. Government, 1904.) Archdall Reid, on the other hand, in a written Tue Wellcome Research Laboratories of the Gordon communication, brings out with admirable lucidity College, Khartoum, which were equipped by the the distinction between degeneracy properly so called munificence of Mr. Henry S. Wellcome, have certainly and the defective development of the individual.justified their existence, judging by the record of work These questions, both of them urgent, we must face.

done during the year February, 1903, to February,

1904, as detailed in the report of the director, Dr. “ In the first place we must improve the conditions | Andrew Balfour. under which the individual develops, and so make The volume commences with a brief description of him a fine animal. In the second place we the laboratories, after which follows an account of the endeavour to restrict as far as possible the marriage of various researches that have been carried out in them. the physically and mentally unfit.” Mr. Reid might demic and mosquitoes plentiful would at once direct

Any medical director stationed where malaria is enhave gone on to say that the former method without his attention to the distribution of the latter, and inthe latter, the improvement of external conditions stitute measures to diminish their prevalence. This. without any

check upon the multiplication of the has been done by Dr. Balfour, and the first article is unfit would merely hasten degeneration, as any

devoted to a description of his observations and adslackening in the stringency of natural selection must

ministration in this respect. Of mosquitoes three inevitably do. Mr. Bateson declines to join in

species are particularly numerous, C. fatigans, an

anophelina, P. costalis, and Stegomyia fasciata. Mosinvestigations carried on by the “ actuarial” method, quito brigades have been organised, and anti-malarial preferring experimental breeding with its more

measures conducted on the lines recommended by Ross, definite results. But is it possible to experiment with and there appears to be every probability that the human beings?

prevalence of mosquitoes will be greatly diminished in Prof. Geddes, in his “ Civics," recommends

Khartoum in the near future. Collections of mosstudents a geographical survey of some river basin quitoes have been received from various parts of

Egypt, the Sudan, and Abyssinia, and have been exin which is displayed the evolutionary process which, amined and named by Mr. Theobald, who contributes beginning with “ hunting desolations ” on the hill- an article descriptive of the species, many of which







are new. Experiments were made on the use of an anilin dye, chrysordine, for the extermination of mos

LETTERS TO THE EDITOR. suito larvæ and pupa. It was found to act satis

[The Editor docs not hold himself responsible for opinions factorily in a dilution of 1 in 30,000, but for practical expressed by his correspondents. Neither can he undertake purposes its use in this strength would be prohibitive to return, or 10 correspond with the writers of. rejected on account both of cost and of its yellow colour. manuscripts intended for this or any other part of NATURE. Biting and noxious insects other than mosquitoes is the No notice is taken of anonymous communications.) subject of the next article, the most interesting find

Electromagnetics in a Moving Dielectric. being G. morsitans, the tsetse fly which carries

Some time ago, when considering the assumption thar nagana, on the Pongo River, Bahr-el-Ghazal, and a

the ether inside a body is quite stationary when a body is few pages are devoted to insects and vegetable para

moved, and that in the application to Maxwell's ethereal sites injurious to crops, the most important being an

equations this involves the use of a fixed time differentiaphis destructive to the dura crop described by Mr.

ation for the ether, and a moving one for the matter. I Theobald as Aphis sorghi (nov. sp.). Cyanogenesis,

argued that the same applied not only to the electric hydrocyanic production, in the dura (Sorghum vulgare) polarisation, as done by Lorentz and by Larmor, but also is another subject briefly dealt with, and of importance, the magnetic polarisation. I told the late Prot. since considerable loss of horses and cattle has some

FitzGerald that to make the extension seemed to be a sort times been occasioned thereby. The dura contains a

of categorical imperative. For it involves no assumption

to how the magnetic polarisation is produced. !! glucoside which yields hydrocyanic acid on decomposition, the cause of which has been ascribed to abnor

the time I made the application to plane waves only

Since then I have extended it to the general case. The mal growth, but may be due to the dura aphis as

principal interest at present lies in the mechanical activity demonstrated by Dr. Balfour.

fundamentally involved in the question of the pressure of Lastly, the general routine work, pathological and

radiation, and electromagnetic moving forces in general. chemical, of the laboratories is summarised, some in- The results confirm the desirability of applying simulat teresting notes are given of the various diseases met

reasoning to the magnetic and to the electric polarisation, with in the Sudan, and the occurrence of eosinophilia in so far as they are relatively simple, and cast light in Bilharzia disease and dracontiasis is discussed. upon the subject.

We congratulate Dr. Balfour on his first year's Thus, let m=VDB be the complete quasi-momentum work contained in this report, which is copiously illus. per unit volume, and M,=VD.B, the ethereal part. Ther trated, some of the coloured plates of mosquitoes and

if the velocity of the matter is u, and of the ether a. other insects being beautifully executed.

motional activity in the absence of free electrification, ur R. T. HEWLETT.

variation of the electrical constants in space) comes to

u(d/dt) + (u.u }(M - M,) + g(d/dt) + 0(9.9) M, i Till the Sun Grows Cold. By Maurice Grindon.

or, in a more developed form, Pp. 113. (London : Simpkin, Marshall, Hamilton,

uddl+up+yu+V. u/(M-M.)+qdidi +90+0+0./M, 12) Kent and Co., Ltd., 1904.) Price 2s. 6d. net.

Here the factor of u is the moving force on the matter, and Though this story is, so far as its main incidents

that of a the force on the ether. It will be seen that in are concerned, of a familiar kind, it differs from

the material part we simply deduct that part of the others in that several of the persons described are

complete M which does not move with the matter. This interested in science. For instance, there is a Sir

makes a great simplification of ideas. To avoid mis onJohn Harpur, who was making important alter- | ception, the pin (1) acts upon all that follows, whereas in ations in his Observatory; he

ardent (2) the first v acts on the M's, but the second and third Astronomer, and F.R.A.S.'; Lady Harpur, again, on the velocities only, as may be seen on comparison “ had a love of flowers beyond that of a botanist,

with (1). although she was adept in the science”; and the It is necessary, however, to point out distinctly the data hero, Ralph Hillary, at one time of his life had a

involved in the above, as the simplification comes about

in a special way. workroom “in which he could follow up chemical

Divide the displacement D and other researches to his heart's content." More- P =CE in the ether, and D, =ce, in the matter, where

E, =E+e, and e=V(u-q)B. Similarly, divide the inover, after Ralph takes as a second wife his early

duction B into Bo=14, and B. =, H,, where H, = H+h, and sweetheart, they engage together in scientific re

n=VD (u-q). The electric energy is U.+ U, = }ED.+ search, and discover a substance of “ extraordinary | E, D, and the magnetic energy is T.+T, = "HB + MB, radio-activity

which they give the

Also, let there be four æolotropic pressures, of Maxwellian Helenium-after Ralph's sister. We cannot say that type, say P, P, electric, and Q., Q magnetic. E. the author has been successful in blending fact and P, =l"; -ED,, meaning a tension l', parallel to E, cumfiction together so that one can scarcely be distin- bined with equal lateral pressure.

The rest

are similar. guished from the other; yet this art is essential to Finally, the two circuital equations are the writer of scientific romance or romantic science.

Vo(H-ho-hi)=D, - Vp(E-e, -e,) = B. (31 A Short Introduction to the Theory of Electrolytic

where the motional electric and magnetic forces are de Dissociation. By J. C. Gregory. Pp. 76. (Lon- completes the data, and from them may be derived the

fined by n =VD,q, n,=VD,u, o, =VqB,, e, =VuB,. This don : Longmans and Co., 1905.) Price is. 6d.

equation of activity This is a useful little book for those students who,

-DVEH +qU,+T, + P + Qo) +u(U, +T, + Pi + Q. after taking a course of systematic chemistry, wish = U+T+00/60)+(U,/6)6+(To'molin+(T,/M, bien + P,9+P, u, i* to know something of the behaviour of electrolytic

Thi solutions. The language and mode of presentation where F and F, are the forces displayed in (2). are simple, and although one might take exception to

meaning is that the left side of (4) is the convergence of many points of detail, the book, on the whole, should

the flux of energy made up of the Poynting flux, the

convective Mux, and the activity of the pressures, whilst prove a trustworthy guide. The headings of the four chapters into which the book is divided afford a

the right side shows the result in increasing the stored

energy and in work done upon the matter and ether, either, sufficient indication of its contents :--chapter i., the both or neither, according to the size of the two velocitin condition of dissolved substances; chapter i., ions The terms involving i, &c., in (4) represent residual and precipitation; chapter iii., hydrogen and hydroxyl activity which may be of different sorts. The commonest ions; chapter iv., electrolytic and general consider- is when the constants vary in space, especially at 3 ations.

boundary. For example, i, = - up.c; if ç, does not vart



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