THURSDAY, SEPTEMBER 21, 1905.

THE EVOLUTION OF MATTER. L'Evolution de La Matière. By Dr. Gustave Le Bon. Pp. 389. (Paris: Flammarion, 1905.) Price 3.50 francs.

DR.

R. GUSTAVE LE BON has written many books. Some twenty volumes, besides papers in current scientific periodical literature, have issued from his pen. History, travels, tobacco-smoke, anthropology, horsemanship, and psychology have in turn attracted his sympathetic interest.

The work before us sets forth Dr. Le Bon's theories of matter and energy, and contains, in a small-print appendix, an abstract of the experimental evidence on which he is content to rest those theories.

According to the author, matter itself is merely a form of energy-probably vortex energy in the luminiferous æther. Matter disintegrates spontaneously in radio-active substances, but also under the influence of certain agencies such as heat or chemical action, which are compared with the spark that fires a barrel of gunpowder. After giving rise to "les produits de la dématérialisation de la matière : ions, électrons, rayons cathodiques, &c.," all things finally pass into “l'élément immatériel de l'univers : l'Éther." By the dissociation of matter, energy is transformed, and "c'est de l'énergie intra-atomique libérée par la dématérialisation de la matière que dérivent la plupart des forces de l'univers."

The chief experimental evidence on which Dr. Le Bon relies may be grouped under two heads :(1) the emission of negatively electrified particles by metals when incandescent and when subjected to the action of ultra-violet light; (2) the slight radio-activity which may be detected in ordinary materials.

The emission of negative corpuscles from metals under the influence of heat and light undoubtedly occurs, though it is not to the author's speculative opinions that we owe the experimental demonstration of the fact. As a speculative hypothesis, the idea that the corpuscles are emitted during the disintegration of the atoms of the metal is perhaps worth bearing in mind. But, on a review of the evidence known at present, it seems unlikely that the removal of these slow-moving negative corpuscles results in the instability of the atom from which they are derived. There is no evidence that an electric discharge through a gas produces new elements, while the ions of liquids and gases, which result from the removal of the corpuscle, again yield the original atom when neutralised. Such processes are to be distinguished sharply from the irreversible changes which occur in true radio-activity, when bodies of atomic mass (a rays) or fast-moving corpuscles (B rays) are projected. In this case, new chemical substances always appear, and the process seems to be unaffected by heat, light, or any other physical or chemical agency. This essential distinction is not noticed by Dr. Le Bon, who assumes that the production of a corpuscle is itself a proof of atomic disintegration.

The author claims that he was the first to show

"Mon premier mémoire sur la radio-activité de tous les corps sous l'action de la lumière a paru dans la Revue Scientifique de mai 1897. Celui sur la radio-activité par les actions chimiques a été publié en avril 1900. Celui montrant la radio-activité spontanée des corps ordinaires a paru-toujours dans la même revue en novembre 1902. Les premières expériences par lesquelles les physiciens aient cherché à prouver que la radio-activité pouvait s'observer avec des corps autres que l'uranium, le thorium et le radium n'ont été publiées par Strutt, McLennan, Burton, &c., que de juin à août 1903.

We may first notice that Dr. Le Bon classes the effects of light under the head of radio-activity. This, it may be argued, is a matter of definition, and the author is at liberty to give a meaning to the word radio-activity different from that adopted by all other physicists. But it is well to point out that many experiments on the electric effects of the incidence of light on metals had been made before the year 1897, notably by Elster and Geitel between 1889 and 1895. Dr. Le Bon may have been the first to suggest that the effects were due to the emission of particles, but no conclusive evidence was obtained until the experiments of J. J. Thomson and Lenard, in 1899, had determined the ratio of the charge to the mass, and identified the particles with those found in kathode rays.

Secondly, doubt has been thrown on the emission of rays by substances undergoing chemical action by the recent experiments of Mr. N. R. Campbell, who has traced some, at all events, of the effects to secondary causes connected with the heat of reaction. Here Dr. Le Bon does not seem always to separate clearly the ionisation which may be produced in a gas by contact with substances undergoing chemical change, and the emission of radiations, more or less penetrating, characteristic of true radio-activity.

Thirdly, in examining the spontaneous radio-activity of ordinary materials, the author seems to underestimate the effect of the minute traces of radium which are now known to be distributed widely. He claims Prof. J. J. Thomson's experiments on the emanations emitted by various natural substances and underground waters as a confirmation of his view that all matter is radio-active. Now, Thomson found that the rate of decay and the phenomena of excited activity in those emanations which he examined closely were about the same as those of the radium emanation, and his experiments should be regarded as an indication of the prevalence of radium rather than of the radio-activity of ordinary materials. It is true that further experiments by Thomson, Cooke, Campbell, Wood, and others have now made it probable that ordinary metals, at all events, are slightly radio-active. But, to eliminate the effects of strongly radio-active impurities, it is necessary to take the utmost precautions, both in the experiments themselves and still more in the interpretation of the results. There seems little evidence that, in either respect, Dr. Le Bon recognised the necessity of such precautions.

It will be gathered that the author takes a point of view which is not that of the majority of physicists who have investigated these subjects. Revolutionary opinions may prove a valuable tonic to the orthodox in physics as in other matters. It is not because he is heterodox that we are not satisfied by Dr. Le Bon's book. It is because he seems to us to fail in grasp of the subject, to confuse phenomena which are essentially different, and to be blind to evidence which does not support his hypotheses.

A belief in the evolution of matter is fast becoming not only possible but inevitable. Dr. Le Bon has written readable speculations about that evolution, and here and there has thrown out an interesting idea; but the evidence on which that belief must be founded is not that put forward by him. His book calls to mind the advice offered by a famous Lord Chief Justice to a brother judge, that it was sometimes safer to give one's conclusions without the reasons which had led to them.

W. C. D. W.

THE FÆRÖES AND ICELAND. The Faeröes and Iceland; Studies in Island Life. By N. Annandale. With an appendix on the Celtic Pony by F. H. Marshall. Pp. vi+238; illustrated. (Oxford: Clarendon Press, 1905.) Price 4s. 6d.

net.

THE

HE name of Mr. Nelson Annandale has been of late years so intimately associated with the Malay Peninsula and its zoology and ethnology that it comes somewhat as a surprise to find it on the titlepage of a work dealing with such totally different surroundings as those of the Færöes and Iceland. It appears, however, that between the years 1896 and 1903 the author spent several summer holidays in these remote islands, and contributed a series of articles on his experiences to Blackwood's Magazine and the Scotsman, and that it is these delightful articles, in a more expanded and elaborated form, with the omission of certain purely technical details, which form the basis of the work before us.

As Mr. Annandale suggests in his opening chapter, most persons probably regard the Færöes as little more than mere Arctic rocks, teeming with sea-birds, in the ocean; and they will accordingly be surprised to learn that, as a matter of fact, although lying nearly a couple of hundred miles to the north-west of Shetland, they enjoy a climate warmer than that of many parts of Scotland, while their vegetation, if rarely more than a few inches high, is as luxuriant as the shallowness of the soil and the winter storms

will allow. The buttercups, too, seem larger, and the bushes of a brighter green, than on the mainland. These islands have also to be regarded as desirable spots, for it appears that although a few years ago they possessed a couple of dozen policemen, the moral of the population has been so excellent that the services of these guardians of the peace were found no longer necessary, and the force has consequently been disbanded. A truly remarkable record!

The first two chapters deal with the people of the Færões and their mode of life, and will be found to contain a number of interesting observations on their ethnography and the implements of the islanders. The invasion of Iceland by the Moors in the seventeenth century forms the subject of a third chapter, but perhaps the most interesting part of the whole book is that dealing with the wonderful bird-cliffs of the Westman Islands, and the clever manner in which the natives capture puffins and other birds in nets. The fulmar appears, indeed, to be very valuable to the Westmaners, supplying them with both food and light. Other chapters deal with Iceland and its products, and the insects and domesticated animals of both that island and the Færöes.

Mr. Annandale deserves, indeed, our most hearty congratulations, and has succeeded in producing a most admirable little work which may be perused with interest alike by the general reader and by those who have enjoyed, or expect to enjoy, the opportunity of visiting the islands he so happily describes. Whether similar congratulations should be extended to Dr. Marshall for his share of the work we are not fully assured. That gentleman seems, indeed, to be under the impression that no one save Profs. Ewart and Ridgeway has written in this country on the origin of the horse. Otherwise he would have scarcely credited the former with being the first to regard Przewalsky's horse as a variety of Equus caballus. Neither would he have omitted to notice that an earlier name than przewalskyi has been. this animal, and also suggested as referable to that Prof. Ewart's E. celticus is probably inseparable from the earlier E. hibernicus. Moreover, he might have pointed out that it is difficult to understand how Prof. Ridgeway's new name of E. c. libicus can stand for the barb, when the Arab horse has long since received a technical name of its own.

OUR BOOK SHELF.

R. L.

Le Système des Poids, Mesures et Monnaies des Israélites d'après la Bible. By B. P. Moors. Pp. 62+1 plate of figures and 6 tables. (Paris: À. Hermann, 1904.)

THE first part of this work consists of an inquiry respecting the numerical value adopted by the the ratio of the circumference of a circle to its Israelites at the time of Solomon for the constant, diameter. M. Moors obtains the greater part of his material for this investigation from the dimensions of the "molten sea" in Solomon's temple, as stated in I. Kings, vii., 23-26, and II. Chronicles, iv., 2-5These dimensions have led some writers-notably Spinoza and Hoefer-to the opinion that the Israelites knew of no nearer approximation to than the whole number 3. The specification of the molten sea is not however, sufficiently complete to determine its shape with any degree of certainty. Some commentators have considered it as cylindrical, others have followed Josephus in ascribing to it a hemispherical form. whilst Zuckermann suggests a combination cylinder and parallelepiped. The author of this work, who is firmly of opinion that the Israelites accepted a value for TM very close to 3.142, has found it necessary in support of his argument to assume that the molten

of

The remainder of the work deals with the system of weights, measures, and coinage in use among the Israelites. Carefully disclaiming any bias in questions theological, he adopts the Bible as the chief authority on the subject of which he treats. The weights and measures mentioned in the Bible are not, however, always very clearly defined, and in attempting to combine them in a homogeneous system we are confronted with apparently hopeless inconsistencies. Owing to this difficulty M. Moors finds it necessary to have recourse to materials of somewhat incongruous character. From a strange medley of midwives, manna and mummies, he evolves, with much ingenuity, a series of metric equivalents for the weights and measures of the Israelites. He claims that his equivalents are confirmed by all those passages in the Bible which contain references to weights and measures. It is interesting to note that his value for the length of the cubit, viz. 443.61 millimetres, agrees very closely with the value obtained recently by Sir Charles Warren (17.64 inches, 448.05 mm.).

=

It is hardly possible to accept the view of M. Moors that the Bible was intended inter alia as a text-book on mensuration. In spite of his laudable effort to throw light on the old Hebrew weights and measures they still remain dim to us. In the region of metrology the Israelites would indeed appear to have baffled the commentator, and to have buried their authoritative (C standards deeper than did ever plummet sound" out of the excavator's reach.

So far as we have checked the numerical calculations made by M. Moors, we have found them invariably accurate. There is, however, an obvious misprint in the last line of his letterpress; "43.5" should read " 43,500."

A Primer on Explosives. By Major A. Cooper-Key, Edited by Captain J. H. Thompson. Pp. xii+94. (London: Macmillan and Co., Ltd., 1905.) Price 18. THIS little book should prove of great value to those for whose benefit it has been mainly written, viz. the local inspectors under the Explosives Act, and those dealers whose trading necessitates the handling and storage of explosives.

No one can better realise the want of some little handbook on the subject than H.M. Inspectors, and it is to meet this want that Major Cooper-Key has written this useful book, which, it is pointed out, is "not a treatise on explosives.' The author gives a short description of the manufacture of the chief explosives, but its great value will be found in the sections devoted to special risks with each class, the methods of packing and storing, and a particularly useful chapter on the general construction and management of a store, the destruction of explosives, &c.

It is certain that a careful study of the book by local inspectors will lead to a better understanding of the whole question of explosives and the Act

generally, and hence to a more intelligent performance of their responsible duties. For those traders and users who have the handling of these goods after they have left the manufactory the book should be equally valuable, and it should do much to lessen the

risk of those untoward accidents which occur from time to time, generally from ignorance of the properties of the bodies dealt with. J. S. S. B.

A Note-book of Experimental Mathematics. By C. Godfrey and G. M. Bell. Pp. 64. (London: Edward Arnold, 1905.) Price 28.

THIS book gives concise instructions for carrying out a number of simple quantitative experiments in mechanics. It is specially suited for students who intend to sit for Army Entrance Examinations, but the excellence of the course outlined renders the book very serviceable for general use in schools; the students get accustomed to fundamental methods of measurement, obtain concrete conceptions of elementary science, and secure much data well adapted to serve as examples and illustrations in a course of practical mathematics. The experiments include measurements of lengths, areas, volumes, weights, specific gravities, fluid pressures, forces, moments, velocities, accelerations, and many other physical quantities. A full and careful list is given of the requisite apparatus and fittings, and the book will be of very great assistance to teachers in the arrangement of a thoroughly sound elementary course of experimental science.

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.] Cause and Prevention of Dust from Automobiles. THE article on the above subject in the issue of NATURE for September 14 (p. 485) is an important contribution to a subject of great interest and importance to the community, but it contains a statement with reference to tar-macadam which in the interests of engineers should, I think, be verified. Speaking of "Tarmac "the writer says, the slag is thoroughly impregnated, so that if the pieces are broken further a tarred surface is still found.'

I have examined many specimens of tar-macadam, including "Tarmac.", I have never found any sign of penetration of tar. I am aware that some believe in this alleged penetration, but it seems to be obvious that any material sufficiently porous to enable tar to saturate it would be totally unfit for road-making.

That tar-macadam, and, of course, "Tarmac," have virtues for motor road-making may be admitted; but this penetration theory is not the reason, and it is a pity that the myth should still exist, as it tends to prevent the trial of other substances far more suitable for roads than furnace slag.

The reason why tarred granites and similar hard stones have not hitherto been found so effective is entirely a matter of surface adhesion. Given a suitable tar mixture, there is no reason why hard, non-porous stone should not be as efficient as slag. Penetration has nothing to do J. VINCENT ELSDEN.

with it.

38 St. Stephen's Gardens, Twickenham.

IN reply to Mr. Elsden, I agree that it is of no use to hold mythical views. I think, however, that he is really mistaken in his views that the slag in Tarmac " is not penetrated by the tar. Possibly it may not be penetrated by the most viscous constituents, but upon examining a broken piece of "Tarmac " I have found that the surface is distinctly darker than that of slag which has not been treated. The difference is very noticeable under the microscope, and if a bit of slag from the interior of a treated portion is heated the tar is readily seen, which fact appears to be conclusive evidence that penetration by the tar takes place. I do not, however, suppose that the penetration is very uniform, as slag is not a very uniform material, and therefore in some parts the effect might not be so evident. W. R. Cooper.

82 Victoria Street, S.W.

seen in a cloudless sky. The enormously brilliant red prominence in the north-east quadrant was an undoubted feature of this eclipse, and nothing like it was seen by me in either the 1898 or 1900 eclipses. From several accounts the landscape was illuminated by this red radiating object, and sunset effects were recorded by other observers.

The corona itself was of the maximum type, streamers radiating in all directions even very near

In the cool (?) of the evening the development of the plates was commenced. Those which promised to have some kind of record on them were taken first. To sum up the results, now that the whole set has been developed, it may be said that we have been far more fortunate than was at first anticipated. prismatic reflector worked by Mr. Butler succeeded in securing an excellent picture of the lower corona, the solar diameter being about 8 inches. The 16-feet

The