ROF. BOURNE says rightly that there is a considerable difference of opinion as to the limits of elementary teaching in comparative anatomy, which he defines as "the science which treats of the architecture of animals." The second edition of his well-known and interesting text-book will be welcomed

really necessary for the comprehension of the great principles of the subject.

Prof. Bourne's view is, as he tells us in his preface, that the more elementary the teaching the fuller it should be, and this view finds full expression in the volume before us, which, we venture to think, is likely to appeal to the advanced perhaps even more than to the elementary student. Protozoa are fashionable at the present day, but it is, perhaps, a pity that Prof. Bourne did not follow what he tells us was his original intention, and cmit some of the types with which he deals so fully. Actinosphærium, at any rate, has very slight claims to inclusion in an elementary text-book. On the other hand, a cordial welcome may be extended to Copromonas, a very valuable new type, of which an admirable account is given, based upon the work of Mr. Dobell.

A few inaccuracies in phraseology might with advantage be attended to in future editions, e.g. "smell and taste are localised patches of end organs (p. 9), but these are minor blemishes which detract but little from the thoroughness with which the author has carried out his extremely useful work.

MODERN MIRACLES.

By the

The Faith and Works of Christian Science. writer of "Confessio Medici." Pp. xi+242. (London: Macmillan and Co., Ltd., 1909.) Price 3s. 6d. net.

The position of biology in the University curriculum is at the present time a very critical one, especially in the case of medical students, for whom this work is expressly intended. The enormous increase in our knowledge of the detailed structure of all the commoner forms of animal life which has taken place during the last few years makes it more and more difficult to select the materials for a first year's course. The introduction of too large a number of types necessitates superficial treatment, while, on the other hand, the too detailed study of only a few types leaves the student without time to follow even the main steps in the evolution of the animal kingdom. He cannot see the wood for the trees. The chief value of the study of comparative anatomy and physiology for the medical student lies in the fact that they help him in the end to understand the structure and functions of the human body, but there is very much in the minute structure of the lower animals which is not necessary for this purpose, and we fear that the insistence upon what many regard as superfluous detail has done much in late years to discourage the study of zoology, not only amongst medical students, but also amongst others who doubt their ability to digest and assimilate (especially for examination purposes) the immense mass of intellectual food set before them. Fortunately so much detail, however interesting in itself, is not

science has taken considerable hold on a section of the community here and elsewhere, and we welcome this book by the author of "Confessio Medici " exposing its fallacies, inconsistencies, and dangers. No one, perhaps, could do this in a more genial manner, but the whole forms a scathing indictment

indeed.

In the introductory pages the author tries with more or less success to put into plain words the contrast between philosophy and Christian science. He then arranges in the form of articles some of the tenets of Christian science taken from Mrs. Eddy's writings, discusses life and Christian science, the reality of disease and the reality of pain, and gives a brief survey of Mrs. Eddy's remarkable career. Next, and most important, the record of the testimonies of healing by Christian science is critically examined. Two hundred recent cases (April-August, 1908) are analysed; the author has taken the trouble to write to many of the patients for additional information, and a more inadequate and unconvincing series could hardly be imagined. This one is healed of "kidney and liver trouble," that one of "stomach trouble," a third of "fever," a fourth of "colds and eruptive fever," and so on. The details are of the scantiest, and, in most instances, the diagnosis is the patient's own. The author concludes from these evidences

'that Christian science accepts all testimonials, even the most fantastic and illiterate. That she embellishes what she publishes. That she evades investigation. That her claim to cure organic disease

breaks down under the most elementary rules of criticism. That she does cure functional' diseases. That she has never cured, nor ever will, any disease, except those which have been cured, a hundred thousand times, by mental therapeutics.''

Two further lines of criticism are pursued by the author. First, he pictures a large hospital given over to the care of Christian "scientists," with its cases

of appendix abscess rupturing into the peritoneum, strangulated hernia going on to gangrene, advanced heart disease getting out of bed and taking violent exercise, and spinal disease hanging on gymnastic bars! Secondly, he has obtained information from various medical practitioners of cases of organic disease going from bad to worse under the "treatment" of Christian "scientists."

The author is no dogmatist; he freely admits the influence of mind over body, that Christian science

may cure hysteria and the liquor habit, that as regards the revival of "spiritual healing "it is for the patient and the family to have what ordinance or ritual they wish to have. No doctor would find fault with that sort of work provided it is kept in its proper place. This aspect of mind renders the book all the more convincing, and we feel sure that it may fill a useful place in refuting the pretensions of Christian "scientists." R. T. H.

SEMITIC MAGIC.

By

Semitic Magic, its Origins and Development.
R. Campbell Thompson. Pp. lxviii+286. (London:
Luzac and Co., 1908.) Price 10s. 6d. net.

MESSRS, LUZAC have produced a useful as well

as well-looking volume as the third contribution to their "Oriental Religious Series" in Mr. R. Campbell Thompson's Semitic Magic." Mr. Thompson's book is an attempt to bring our knowledge of Arab, Hebrew, and Babylonian (Assyrian) magic into line with the scientific treatment of the demonology and witchcraft of other peoples which the labours of many devoted workers have given us during the past half-century.

It is not too much to say that the field of Semitic magic has hitherto been somewhat unduly neglected by writers on the subject. Probably shyness of dealing with a subject which must owe so much to a correct interpretation of the cuneiform texts has had much to do with this fact. A knowledge of the necromantic ideas of the Jews and the Arabs, especially of those of the former people, we have always possessed in abundance, but Semitic magic without Babylonian and Assyrian magic would indeed be Hamlet without the Prince of Denmark, and up to the present time general anthropologists have rightly been diffident of their power to collate adequately material of which they have no first-hand knowledge with the results of their study of the necromancy of the Jews and Arabs. It was first necessary that a cuneiform scholar should be found with an active interest in the general subject, and a competent knowledge of the other anthropological material, not only from the rest of the Semitic nations, but from the whole of the primitive world.

Mr. Thompson, who is an Assyriologist with a general knowledge of anthropology and a special interest in the subject of magic, has essayed to fill the gap; and we think that as a first essay he has done so very successfully. His book is not an exhaustive treatise; it can be regarded simply as an introduction to the subject, based from the Semitic side ultimately ligion of the Semites," and from the general side on Robertson Smith's epoch-making book, "The Relargely on the work of Frazer. But at the same time, hesitate to criticise the work of his models when he Mr. Thompson is an original thinker who does not thinks they are wrong, and to draw new conclusions from the large amount of new material which he now places in our hands, derived from his own Assyriological knowledge. Later on Mr. Thompson may perhaps produce a larger work on the subject, to which his present volume will serve as a preface. As it stands, his book is an authoritative contribution to anthropology, which will be found of very great use by all students of the beliefs of primitive mankind.

Mr. Thompson lays great stress upon the subject of tabu, of the existence of which he finds constant evidence among the Semites, while demoniac possession, sympathetic magic, and the specially Semitic ideas of the Atonement, Sacrifice, and the Redemption of the Firstborn, all have chapters specially devoted to them. The long quotations which he gives from the cuneiform texts are of great interest, and enable us to form an adequate idea of the great part which magic played in the daily life of the oldest civilised peoples of the ancient world.

OUR BOOK SHELF.

British Rainfall, 1908. On the Distribution of Rain in Space and Time over the British Isles during the Year 1908 as recorded by more than 4500 Observers in Great Britain and Ireland, and discussed with Articles upon Various Branches of Rainfall Work. By Dr. Hugh Robert Mill. Pp. 100+304; with maps and illustrations. (London: Edward Stanford, 1909.) Price ios.

THE author has stated elsewhere that the perfect rainfall map is a thing of the future, many preliminary studies being necessary before it can be drawn. The irregularity of rainfall and its dependence upon orographical features require a very large number of stations, and observations made during the same period for at least thirty or thirty-five years for determining its average annual distribution and variation. By the energy of the late Mr. G. J. Symons, the founder of the British Rainfall Organisation, and his successors, the British Isles can boast of a system of rainfall observations quite unique and unrivalled by that of any other country; the data published yearly in British Rainfall supply invaluable materials for general discussions, and, in fact, have been frequently utilised by various authorities. Part i. of the present volume, the forty-eighth of the series, contains articles by Dr. Mill on new recording rain-gauges, by Mr. A. Lockwood on rainfall observations in Snowdonia, and others; also records of evaporation and percolation, duration of rainfall at various stations, and other matter. Part ii. includes, inter alia, observers' weather notes for days, months, and the year, heavy rains for short periods and for days, monthly and

46

seasonal rainfall, and a general table of the annual rainfall at all stations. There is also a coloured frontispiece map showing the relation of the rainfall of 1908 to the average of 1870-99. The rainfall of Scotland and Ireland, generally, was practically normal, that of England and Wales rather more than one-tenth less than the average. Only a small part of England and Wales, but a large part of Scotland and Ireland, had more than the average; parts of the south of Ireland, south-west and east of England and east of Scotland were very dry. The greatest annual amount recorded was 2373 inches, at Llyn Llydaw (Snowdon); the least, 15'6 inches, at Bourne (Lincolnshire). Among the changes introduced in this volume may be mentioned (1) that, in discussing monthly rainfall, maps of the actual fall are given side by side with those showing the percentage difference from the normal; (2) much fuller treatment of the sections relating to heavy falls on rainfall days and in short periods. Although efforts have been made to economise space, and no part is a repetition of any previous issue, the present volume is larger than any of its predecessors, and, we think, compares favourably with them.

La Mesure rapide des Bases géodésiques. By J. René Benoit and Ch. Ed. Guillaume. Quatrième édition. Pp. 228. (Paris: Gauthier-Villars, 1908.) THE invention of invar, the nickel-steel alloy with a small or zero coefficient of expansion, in 1897 imported new conditions into determinations of length. The great value of this invention for the measurement on the ground of the base-lines of a survey was at once apparent, and during the next year the new method was tried by the joint Russo-Swedish expedition in Spitsbergen. The results obtained equalled the most sanguine expectations. Not only was a high limit of precision attained, but the rapidity of the work, as compared with the old methods, was enormously enhanced. It was obvious that the geodesist had in his hands a new tool which greatly accelerated the most laborious portion of his operations, and at the same time gave him a degree of accuracy at least equal to that hitherto achieved with far more cumbrous apparatus.

These results came into prominent notice at the International Geodetic Conference held at Paris in 1900, and a further and more minute investigation of the whole problem was undertaken by the Comité international des Poids et Mesures.

At the meeting in 1905 a report was furnished by the present authors, to be expanded into a more complete form for presentation to the Geodetic Conference of 1906. The large demand for copies of this report, and the fact that the new method has now been

adopted by almost all surveys having any pretensions to execute work of the first order, have induced the authors to put the record of their investigations into a permanent and convenient shape. Of the present little volume we can only say that it is one that must be in the hands of every geodesist. It contains, in a succinct form, the general theory of measurements by wires hung freely between supports, a short discussion of the physical properties of invar, an account of the testing and standardisation of the wires and of their possible distortions under different conditions of tension, temperature, repeated windings and unwindings, and, in general, their stability under the practical conditions of their employment in the field. This is followed by a description of the auxiliary apparatus used for base measurement, all of a very simple character, and a full account of the routine of the field work and of the calculations for the reduction of the measures to the horizontal, including the necessary tables.

A summary of the actual results attained in practice shows that a rate of measurement of about 5 kilometres per day can be kept up with a limiting error of between 0 and 1000000. With special precautions a still higher degree of apparent accuracy can be reached, but such appearance is largely delusive, and in geodetic work would soon disappear in the angular

measures.

We congratulate the authors, not only on their most valuable investigations, but also upon the excellent form in which their conclusions are presented.

E. H. H.

Bibliotheca Geographica. Jahresbibliographie der gesamten geographischen Literatur. Herausgegeben von der Gesellschaft für Erdkunde zu Berlin. Bearbeitet von O. Baschin. Band xiv. Jahrgang, 1905. Pp. xvi+545. (Berlin: W. H. Kühl, 1909.)

THIS is one of those publications (and there are not a few) for which British geographers may well be grateful to German. We do not produce many works of this kind-works which can hardly bring profit sufficient to reward the labour of their compilation. The Bibliotheca Geographica" is a wonderfully full bibliography of geographical books and papers published, in all parts of the world, during the year 1905 -it is not to be wondered that the volume bears a date of issue four years later, when the magnitude of the task of tracing such a vast number of publications is considered. General treatises on the various scientific branches of geography are given first; after these there follows what occupies the bulk of the volume-a bibliography according to topographical divisions. Each topographical division is minutely subdivided according to special subjects, an arrangement which partially disarms the criticism that the entry of a publication under its own title or the name of its author seems somewhat arbitrary.

It is doubtful, however, whether any large biblioSome graphy would entirely escape this criticism. difficulty, again, is evidently felt with regard to the entry of individual papers out of collected volumes. Thus, when the report of a research committee of the British Association is entered only under the name of the secretary of the committee, it may be doubted whether this method gives the reader the best chance of finding the reference. On the other hand, crossreferences are provided from one subject subdivision to others of a kindred nature, and at the end there is an authors' index, so that one cannot but recognise that the system of the whole work is well-nigh perfect. Moreover, the entries, so far as can be judged, appear to be admirably accurate.

By J. W. Ladner. The Invicta Number Scheme. (London: George Philip and Son, Ltd., n.d.) Handbook, price 8d. net; Number Board, price, with plain edges, 6s. 6d. per dozen; with edges, clothmounted, 8s. 6d. per dozen.

THIS device is a method found useful by a practical schoolmaster of experience in teaching the fundamental principles of arithmetic by constant reference to the decimal system of notation. The plan utilises not only the ears, but the hands and eyes of the children. Though many original teachers will have developed equally good expedients for rendering their lessons in arithmetic practical, interesting, and intelligible, the scheme may be recommended to the attention of teachers who have not as yet adopted concrete aids in their instruction. It is now very generally agreed that children learn best by doing, and Mr. Ladner's method of teaching will certainly assist the children to arrive at the rules they have to learn from the results of their own experiments.

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.]

Magnetic Storms.

In his article upon the recent magnetic storm (NATURE, September 30) Dr. Chree writes: Another difficulty in regarding the phenomena of magnetic storms as entirely and directly due to the action of electrical currents associated with aurora is that it is a frequent occurrenceas on the present occasion-for the horizontal force to be considerably depressed below the normal value when the storm has apparently ceased and for some considerable time thereafter. It is possible, of course, that the external currents have partly demagnetised the earth, or at least modified its distribution of magnetism, and that there are recuperative tendencies tending to cause reversion of what is for the time being a more stable distribution, but if this be the true explanation the demagnetising action and the recuperative tendencies are presumably in action during the course of the storm, and profoundly modify the magnetic phenomena."

I wish to add to Dr. Chree's words the remark that this phenomenon of decrease in horizontal intensity is nothing but part of the phenomena I described a long time ago, and about which I exchanged opinions with Dr. Chree in Terrestrial Magnetism.

Later on I found occasion in several publications again to deal with those phenomena of "Post-turbation "; also recently, at the meeting of the Helvetic Association of Natural Science at Lausanne.

In a short statement I directed attention to the fact that the results of my investigations on magnetic perturbation are in accordance with the splendid results and theories of Birkeland and Størmer.

My results were shortly as follows:

A force of disturbance is always present; it strongly increases when a storm appears, decreasing afterwards. The horizontal component of this force is chiefly directed to the magnetic south, i.e. along the meridian of the regular magnetism of the globe, thus lying in the plane through the magnetic axis and the station.

The vertical component, on the contrary, mostly has the same direction as that of permanent magnetism, i.e. downward in the northern hemisphere. Its character and sign are much less constant than those of the horizontal component.

The regular post-turbation is most frequent at lower latitudes.

An extensive study of all the storms recorded at Batavia has taught me that the post-turbation often emerges in a negative sense (northerly), but shortly after turns and reaches its maximum positive value. Afterwards it decreases at a slower rate, and this decrease continues until a new storm (it may be a very small one) appears. I found that successive quiet days show that same decrease. This is the same that Dr. Chree also detected, and called non-cyclic variation.

At Lausanne I pointed to the fact that this kind of disturbance corresponds to Birkeland's class of positive equatorial disturbances. He also found negative disturbances, but from my statistics it is evident that they are much less frequent than the positive.

As to the cause of these positive equatorial disturbances, Birkeland, according to his experiments with his terella and the theoretical calculations of Størmer, accepts currents of electrons flying around the magnetic equator of the earth. As for the negative ones, he accepts electrons which move also in that plane, but through a loop in their orbit, thus having a contrary direction.

If we accept the cause of the post-turbation to be the presence of an electric current, this current must be extraterrestrial, because the vertical component generally increases when the horizontal one decreases.

The less regular character of the vertical component may be explained by the currents of induction raised inside the 1 "Die magnetische Nachstörung," Met.orclogische Zeitschrift, 1895.

globe. Accordingly, an effect of demagnetisation of the earth seems to be improbable.

From the inspection of thousands of magnetic curves recorded at Utrecht, Batavia, and other non-Arctic stations, I received the impression that the increase and decrease of the post-turbation are fairly regular, the rapid oscillations being superposed on this variation.

No doubt these rapid oscillations are caused by currents of electrons nearly approaching the earth, and this will happen more frequently in the polar regions than in the equatorial ones. Thus the action of the ring current will show itself more distinctly at stations at lower latitudes, the ring being nearer to them than to stations at higher latitudes, and it will be less disturbed by other currents coming very near to the earth.

Dr. Chree concludes his article with wise words, saying" To many minds subscription to some theory may be a necessity for intellectual comfort, but in the case of magnetic storms reservation of judgment appears at present the more scientific attitude.

I fully agree with him in this respect, but I think he, who himself has contributed so much to the science of terrestrial magnetism, will agree with the call for more activity. The work of Birkeland and Stormer is splendid indeed, but it is only in the power of international cooperation, such as in the year 1882-3, to unravel all the problems of magnetic disturbance.

We should repeat that work, considering that at present we are able to do so much better and more completely than our predecessors were in those days.

Concentration of our efforts on special problems, I think, would be more effective than the unsystematic accumulation of material nowadays.

The crowding of permanent magnetic observatories in Europe may be favourable to the solution of minor problems; it is a hindrance to that of the fundamental ones, because it absorbs too great a part of the powers at our disposal. W. VAN BEMMELEN.

The Hague, October 13.

Homogeneous Corpuscular Radiation. WHEN a metal plate is subjected to a beam of Röntgen rays, a corpuscular radiation is in general emitted, in addition to the secondary radiation of the Röntgen type.

This corpuscular radiation has been investigated by various experimenters. They have shown that the intensity and the absorbability of this radiation vary when different metals are used, and that they are also dependent upon the degree of "hardness" of the exciting radiation. In particular, Cooksey has recently shown that the corpuscular radiation excited by a "hard primary beam is homogeneous, while that excited by a "soft" primary is hetero

geneous.

But the primary beams used in these investigations were necessarily heterogeneous, and it is therefore impossible to decide with certainty which components were chiefly concerned in producing the phenomena under investigation. It has been shown in various papers by Prof. Barkla and myself that a series of secondary Röntgen radiations can be obtained from the group of metals the atomic weights of which lie between those of chromium and silver, each radiation being homogeneous and having a perfectly definite coefficient of absorption by a given metal, e.g. aluminium. The absorption coefficients of the beams from the different members of the series vary greatly in value; thus for the secondary radiation from iron the absorption coefficient by aluminium is 240, while for that from silver it is only 6-7. I wish to place on record a summary of the results of some investigations I have made upon the corpuscular radiations excited in various metals when these homogeneous secondary beams are employed as primaries instead of the heterogeneous primary beams used by previous investigators.

(1) It had been shown by Prof. Barkla and myself that the penetrating power of the incident primary radiation must exceed that of the homogeneous secondary Röntgen radiation characteristic of a metal before the latter is excited. Using homogeneous beams, I have shown that when the primary beam is only just more penetrating than the secondary Röntgen radiation characteristic of the metal, the intensity of both the secondary Röntgen radiation and