of the rare elements, and some of the more important are given. Zirconium in particular has properties that render it valuable in many ways; the metal has a very high melting point, and is so hard that it can be used as an abrasive and for glass-cutting; the oxide is largely used in the manufacture of crucibles and furnace linings, and for many other purposes; it has even been suggested as a toilet powder. Among the properties of the metals of the cerium group is the power of forming pyrophoric alloys; cerium with 20 per cent. of iron is said to form an alloy which gives showers of sparks when scratched or struck, and "lighters" made from this and similar alloys are already in use.

The last chapter of the book is devoted to a discussion of the technical possibilities of titanium. and its compounds; there are many uses suggested for this interesting element; its very high melting point, 2350° C., renders its employment in metallurgy difficult unless first alloyed with iron, as ferrotitanium; from this many valuable alloys have been formed.

Broadly stated, Freud's psychological system is based upon a fundamental distinction between two classes of memories and mental tendencies, viz., ordinary memories and tendencies and those that have for one reason or another been repressed. The latter are those involved in mental conflicts and accompanied by pain. They constitute the true "unconscious" of the mind. The other memories are classed by Freud as "pre-conscious." Unconscious memories and mental tendencies retain their original intensity, and although outside of consciousness continue to act, and from time to time affect consciousness. "Like the shades in the Odyssey," says Freud, "they come to life again as soon as they have drunk blood." When especially intense, or when the repressing power of the mind is in one way or another diminished, they may produce the symptoms of hysteria and of other forms of mental disease. But they are also the cause of dreams in normal persons, and of the apparently unintentional mistakes in speech, writing, and other actions, to which we are all more or less subject when our attention is distracted. Freud tries to sustain this latter view in his "Psychopathology of Everyday Life." He contends that the method of psychoanalysis,1 or free association, demonstrates conclusively that such slips of memory, speech, and writing are really intentional, and due to the concomitant working of unconscious mental tendencies. In his view the problem for psych

ABNORMAL PSYCHOLOGY.

(1) Psychopathology of Everyday Life. By Prof. S. Freud. English Translation with Introduction by Dr. A. A. Brill. Pp. vii+342. (London: T. Fisher Unwin, 1914.) Price 12s. 6d.

net.

(1) THE

(2) The Unconscious. The Fundamentals of Human Personality, Normal and Abnormal. By Dr. M. Prince. Pp. xiv +549. (New York: The Macmillan Co.; London: Macmillan and Co., Ltd., 1914.) Price 8s. 6d. net. HERE has been a rapid growth of interest, during recent years, in the theoretical explanation and practical treatment of mental diseases, especially of those so-called "borderland cases between the normal and the definitely insane. The problems involved have aroused vigorous controversy, and the most conflicting views have been put forward by different schools of thought. Among the exponents of these various doctrines two of the most distinguished are Prof. Freud, of Vienna, and Prof. Morton Prince, of America.

why we come to forget, and his own solution of the problem is that we forget the unpleasant, except when special factors make this forgetting impossible.

The theory is a comprehensive one, and not so easy to refute as might at first sight appear. There can be no doubt that in quite a number of cases repression plays an important part in the forgetting of unpleasant incidents, and that unconscious mental tendencies sometimes prove their existence by disturbing our speech and other acts. But the exceptions are numerous, and even some of the cases which Freud himself analyses at length seem to admit of other explanations. The book is extraordinarily interesting, however, and full of hints for the student of human nature.

(2) Dr. Prince's book is an excellent introductory text-book for medical psychologists. It sets out very clearly the various senses in which the word "unconscious" has been used by different writers, and shows how important the concept, when adequately defined, is for abnormal psychology. Morton Prince distinguishes what he calls the co-conscious from the unconscious. 1 See "What is Psychoanalysis?" NATURE, February 5, 1914.

The former is the split-off or dissociated consciousness demonstrable in cases of hysteria, etc., the latter is to be thought of best in physiological terms. He recognises the existence of repression, in the Freudian sense, in certain cases, but is unable to verify its universal existence in pathological cases. Many of the instances which he quotes are also strong evidence against Freud's view that sexual experiences, especially those dating from early childhood, are invariable factors in the production of neuroses.

Towards the end of the book there are some

excellent chapters on instinct, emotion, and sentiment, which form an important contribution to the question of the nature of personality. The book will be found extremely helpful by those medical men who desire a well-balanced statement of the facts and theories of medical psychology at the present day. WILLIAM BROWN.

PASTEUR AND PREVENTIVE MEDICINE. (1) Pasteur and after Pasteur. By Stephen Paget. Pp. xii+ 152. (London: A. and C. Black, 1914.) Price 3s. 6d. net. (2) On Pharmaco-Therapy and Preventive Inoculation applied to Pneumonia in the African Native, with a discourse on the Logical Methods which ought to be Employed in the Evaluation of Therapeutic Agents. By Sir A. E. Wright. Pp. xii+124. (London: Constable and Co., Ltd., 1914.) Price 4s. 6d. net.

(3) IN

N this volume, one of a series of manuals on medical history, Mr. Stephen Paget, with his usual facile pen, outlines the life of Pasteur. Commencing with his early years, we have a glimpse of Pasteur's home and of the ideals which influenced his whole life :

"Work hard, honour your country; put spiritual things above material, and other people before yourself; have courage, have patience.' "Work; love one another," he writes to his little sisters. "Once you have got into the way of working, you cannot live without it. Besides, everything in this world depends on it."

An excellent description follows of his chemical researches, his study of tartaric acid and of the tartrates, and the foundation of stereochemistry therefrom. In January, 1849, Pasteur is offered and accepts the professorship of chemistry at Strasbourg :

"Friendship met him on the threshold, and Love was waiting for him just across it. Friendship was young M. Bertin, who had been at school with him, and was now professor of physics in Strasbourg: Love was Marie Laurent, a daughter of the rector of the academy. Within a month, he had sent to her father his formal pro

posal of marriage. At the end of May they were married. She was everything to him: without her, his work would never have been accomplished: he would have died, long before he did, writing of her: the two lives are one, from 1849 to the day he died."

under the strain of it. To write of him, is to be

Pasteur's studies on fermentation and its influence on Lister's work are next discussed, and a beautiful little picture is given of Lister, the

man :

"In 1893, the death of Lady Lister took the . . . To recall him, is to delight out of his life. think, first, of the dignity, gentleness, and refinement of his face its delicate colouring, the tranquil, almost dreaming, look of his eyes. . . . He smiled, not laughed a smile of singular beauty, but hard to interpret. . . . Tired, lonely, and, long before he died, broken in health and in the enjoyment of living, one thinks of him, still as a man serene through controversy, a spirit of invincible patience and of radiant purity."

One of the traits of Lister's character, which the reviewer likes best to remember, was his intense concern for the welfare of the patients who came under his care-an untoward incident was a real grief to him.

Subsequent chapters deal with Pasteur's other researches diseases of silkworms, anthrax, chicken-cholera, rouget-culminating in his work on rabies, soon after which he began to fail :—

"Then came enfeeblement, a year of quiet resignation; and, in September, 1895, his death. It is recorded of him that he died holding the crucifix in one hand, and in the other his wife's hand. Here was a life, within the limits of humanity, well-nigh perfect.'

All that is mortal of the great master rests— most fittingly-in the beautiful little chapel in the Pasteur Institute, Paris.

Pasteur's work is fundamental and must be regarded as the starting-point of modern bacteriology and of experimental immunity and preventive medicine. Mr. Paget is able from a consideration of all that has since been accomplished in the prevention of diphtheria, plague, cholera, typhoid, and yellow fevers, malaria and Malta fever to show how much we owe to the genius of Pasteur.

We heartily congratulate Mr. Paget on his book, which is deeply interesting, and holds the

attention from start to finish.

(2) Three topics are dealt with by Sir Almroth Wright in this book: first, the use of an organic copper compound "optochin" for the treatment of pneumonia; secondly, the nature of the pneumonia which attacks the native labourers in the

Rand mines, and the employment of prophylactic inoculations to prevent it; and thirdly, a discussion of the logical methods which ought to be applied

in inquiries into the efficacy of therapeutic agents as applied in actual practice. The last-named would perhaps have been better published separately, and need not be further considered here.

As regards "optochin," it is found that this drug exerts a specific bactericidal action on the pneumococcus in high dilutions in serum as well as in watery solution. It has been successfully used as an application in local pneumococcic affections, and though some have been favourably impressed with it in the treatment of pneumonia, others have not found it to be of value. There is also some

risk to eyesight in its use.

The pneumonia of the Rand was found to be a pneumococcal infection, and the native seems naturally to possess much less immunity towards the pneumococcus than does the white man. Various trials were made of pneumococcus vaccine as a preventive of pneumonia, and it is finally recommended that a dose of 1,000 millions of pneumococci cultivated in glucose blood broth might be appropriately employed as an ordinary prophylactic dose, as this was found considerably to reduce the incidence of pneumonia among those treated, as well as reducing the mortality if pneumonia occurred among them.

A very large amount of experimental work was carried out in this inquiry by Sir Almroth Wright and his collaborators, and the manner in which the results were controlled and are tabulated are models of what a scientific investigation should be, and form a valuable contribution towards the control of a disease which causes serious loss of life, as well as being one of considerable economic importance in the Rand. R. T. HEWLETT.

ELECTRICAL ENGINEERING. (1) American Handbook for Electrical Engineers: a Reference Book for Practicing Engineers and Students of Engineering. Compiled by a staff of specialists. Harold Pender, editor-in-chief. Pp. xviii+2023. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1914.) Price 218. net.

(2) Electrical Engineering in India: a Practical Treatise for Civil, Mechanical, and Electrical Engineers. By J. W. Meares. Pp. xxxvi+517. (Calcutta Thacker, Spink and Co.; London: W. Thacker and Co., 1914.) Price 15s.

(1) IN

N its thousand pages this "American Handbook" contains information on an enormous variety of subjects arranged alphabetically from "Abbreviations" to "X-Rays." The work is a sort of combination of a library of text-books with a collection of formulæ and data. In the latter department, which must be regarded as its true field, the book will be found of great service

to electrical engineers, but the utility of the textbook portion is, perhaps, open to doubt.

Each section appears to have been written by a man having a thorough and practical knowledge of the subject, and the theoretical and descriptive matter is excellent so far as it goes; where it bears directly on the tabulated matter it is also most useful. But the necessary limitations of space prevent it from being anything like a satisfactory substitute for the detailed text-book. We get just a very brief summary of the leading facts, but we are also given references to other books in which fuller information can be obtained.

Although we would not agree with everything contained in the book (for instance, we do not approve of "abohms," "abamperes," and so on, and do not even admit any necessity for the socalled "absolute" systems of units), we must say that the volume is a useful accessory to the electrical engineer's desk or library.

(2) This book contains a considerable amount of information on electrical matters with special reference to the conditions as to climate, cost, and legislation as they exist in India, but we have some difficulty in imagining a class of engineers to whom it will be really useful. The elementary matter is too scrappy, and too much jumbled up to be of service to a beginner, or even to one who has forgotten; to the man who knows already it would be sheer waste of time to read it.

There is much descriptive matter, but there are very few illustrations; without them the written matter is almost worthless. Most engineers will, we think, prefer a good standard text-book, of which there are a few, for getting up the elementary theory, and one of the well-known "pocketbooks" for tabulated data.

DAVID ROBERTSON.

OUR BOOKSHELF.

English Folk-song and Dance. By F. Kidson and M. Neal. Pp. vii+178. (Cambridge: At the University Press, 1915.) Price 35. net.

It is only in recent years that with the active collection and study of European folk-lore the folksong and folk-dance have begun to receive the attention which they deserve. The collecting of English folk-songs, begun by the Rev. J. Broadwood in 1843, has since that time been actively prosecuted by Miss L. Broadwood, W. Chappell, Dr. Barrett, and Mr. Baring Gould. In 1898 the Folk-song Society commenced its labours, and has year by year added to our knowledge of British and Irish folk-music. A summary of the progress already made and instructions to the collector were badly wanted. This has now been supplied in the present book, which deals satisfactorily with the problem of the origin of folkmusic, and fully describes the methods of nota

tion. The songs of the folk are classified under the heads of narrative ballads, love and mystic songs, pastorals, the songs of the poacher and the highwayman, the soldier and the sailor, the pressgang, hunting, sporting and labour songs, carols, singing games of children, the popular street ballad, and the broadside.

As for the folk-dance, much of the knowledge which we possess is due to the enthusiasm of Mr. Cecil Sharp, who has hunted down the veteran dancers, and taught them how to instruct the minor societies which have been started in almost every large centre. The authors deny that the Morris dance is connected with the Moors, and prefer without good reason a Celtic derivation which makes it to mean "noble." The suggestion that it may be in part due to the Salii or leaping priests of Rome is hazardous; there is more to be said for the theory which connects some of the figures with a primitive sun-worship. The sworddance seems to be derived from some primitive rites of fertility. The manual is a good introduction to the subject, and the bibliography and illustrations leave little to be desired.

Masonry as Applied to Civil Engineering.

By F. N. Taylor. Pp. xi +230. (London: Constable and Co., Ltd., 1915.) Price 6s. net. THE early part of this book contains descriptions of the various kinds of stones used in civil engineering, together with the methods of working and handling them. This portion cannot be described as altogether complete in itself; there are many references to another book by the same author. There is a certain off-hand manner in the treatment which has led to one, at least, unfortunate result. On p. 23 calculations appear giving the load which can be raised by a set of Weston's blocks when a given pulling force is applied. No allowance has been made for friction, hence the result of the calculation is altogether misleading.

In the later portions of the book the author deals with retaining walls, dock walls, dams, bridges, towers, monolithic and block concrete construction, shoring, and underpinning. It is probable that the reader will derive more benefit from the descriptions and drawings given in these portions than from the very brief theoretical discussions and calculations. On p. 43 there is an illustration showing a surcharged wall, together with a few lines of description supposed to indicate how to obtain the thickness of the wall. There appears to be some omission in the illustration; it is impossible to grasp the author's meaning. The treatment of the wedge method on p. 45 is imperfect, and again there appears to be omissions in the illustration.

We

In general, the author gives formula without any explanation of how these are derived. do not think, therefore, that the book is likely to meet the requirements of modern students, who, for the most part, desire to be perfectly clear regarding the derivation, limitations, and assumptions involved in any formula which they are called upon to use in design.

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 Nature of Gas lons.

OUR knowledge of the nature of gas ions is derived mainly from measurements of their mobility in an electric field. Experimental evidence has shown that as the pressure (p) is altered the mobility (k) of the ion alters generally in accordance with the law, pk constant; when this law holds good it is safe to conclude that the ion remains unaltered at the different pressures. One of the most interesting results of experiment is that in the case of the negative ion formed in air the product pk increases as the pressure is diminished below about 10 cm.; this result indicates a simplification in the nature of the negative ion at the lower pressures. Prof. Townsend and his students have examined this phenomenon in great detail, and have come to the conclusion that the velocity (v) of the ion should be expressed as a function of the field (X) and the pressure (p) in the form

"=(X/p), indicating that the nature of the ion depends on the field and the pressure. In his recently published treatise Prof. Townsend concludes that the negative ion in a dry gas is in general a cluster of molecules which for a certain range of electric forces and pressures passes through a transition stage until finally, when X/p exceeds a certain value, the negative carriers are practically all electrons.

In some experiments recently undertaken to determine the mobilities of the ions formed by the radiation from polonium in thoroughly dried air, I have been led to conclusions essentially different from those now generally held. From a pressure of one atmosphere down to about 8 cm. the results were normal; at pressures below 8 cm. the negative carriers were found to consist of two kinds, electrons and ions, the former increasing in number relatively to the latter with diminishing pressure. In no instance was there any evidence of an intermediate or transition stage, the separation between the faster and the more slowly moving carriers remaining throughout clear and distinct. I was able to measure the velocity of the negative ion at all stages until resolution between the two kinds of carriers was no longer practicable, and it was ascertained that the value of pk remained constant from one atmosphere down to the lowest pressure employed (1/7 mm.), indicating that the negative ion remains unaltered in nature over this wide range of pressures.

The fact that electrons exist in dry air at the lower pressures is, of course, well known, but at a pressure of 12 mm. the ions constitute at least 80 per cent. of the negative carriers and at 1/7 mm. more than 50 per cent. The proportion of ions and electrons depends solely upon the pressure, the effect of the field being for the most part small or negligible. For the negative ion at all pressures v was found to be directly proportional to X/p; there seems to be no necessity for introducing any unknown function of X/p.

The fact that the electrons travel through several centimetres of a gas at pressures as high as 8 cm. without attaching themselves to neutral molecules is remarkable, and seems to imply that the distribution of carriers between ions and electrons must be determined immediately after the act of ionisation; it would appear that the electron has to be fired into the mole

THE terms "anadromous and 'catadromous" are employed to distinguish fish which leave the sea to spawn in fresh water and fish which migrate from fresh water to the sea when they reach maturity. Gilson, in his paper, "L'Anguille" (1908, Ann. d. l. Soc. roy. Zool. et Malacol. d. Belgique, T. 43), proposed that the words should be used to define migrations to and from fresh water. The salmon, for example, is catadromous as a smolt, anadromous as a grilse, and so on. But unless new terms are to be created the words must be given a much wider significance than Gilson has suggested. The migrations of fish from the lower part of a river to the higher reaches, from a river to a stream, from the deep region of a lake to the shallows only differ in degree from the anadromous migration of the salmon. It cannot be said either that there is any difference requiring a new term in the migration of a fish from the sea into the lower part of a river or into an estuary. A fish which migrates from relatively deep water to the coast may also be said to have made an anadromous migration. There are species which may spawn in fresh or brackish water, and species which may spawn in salt or in brackish water. In short, it may be said that fishes present every degree of anadromous migration from mid-ocean to the upper limits of streams, and corresponding catadromous migrations. It is now proposed, therefore, that these words should be used to indicate the direction of the migration, however small or great that migration may be, whether passive or active, pelagic or demersal, seasonal or spawning.

But even with the wide meaning here suggested the words cannot be applied to an important feature of migrations in the sea-migrations brought about by current. The Gulf Stream is utilised by fish and other organisms for the conveyance of eggs and larvæ and young to, or towards, the continent, and its branches are no less importantly taken advantage of to convey the products from the spawning ground to a region which may be at some considerable distance. The drift may often be said to be an anadromous one, but it is sometimes catadromous, and frequently could not be defined by either term. The migration of the

mature fish is in contrast to the drift of the larva.

may

This be illustrated by reference to a species not a fish-the common edible crab, Cancer pagurus. The crabs on the east coast of Britain migrate, seasonally, catadromously from the coast for winter and anadromously to the shore region for summer. The mature females after ecdysis, sooner or later become ripe, and in response to the impulse thus conveyed migrate northwards along the coast. During or after this migration they become "berried." The larvæ, when liberated, are planktonic, and are carried by the current to the south. If there were, as there is some

แ

degree of evidence to show that there are, particular regions which present large associations of berried females, the young crabs would reach the bottom most numerously in areas to the south, which may be said to be related to the regions where the larvæ are liberated. Thus with regard to this species there is a migration against the current of the mature females and a

migration with the current of the larvæ, and these migrations are clearly quite distinct from the seasonal movements which characterise the species at the other periods of life.

The relationship of the spawning ground to the region where the demersal fry are deposited is better defined in the case of many of our species of flat fish and round fish, since it results in the formation of schools of seasonal migrants.

To define these and other migrations which are intimately associated with currents it is necessary, therefore, to introduce two terms which will serve to indicate movement against the current and with the current. My colleague, Prof. J. Wight Duff, recommends a Latin root, natare. The words suggested therefore are contranatant, swimming against the current, and denatant, swimming or drifting with the current. The words contranatation and denatation are also available to indicate the act or habit of migration against or А. МЕЕК. with the current. Marine Laboratory, Cullercoats, Northumberland.

A Mistaken Butterfly.

In this connection the case should be recalled of the Cleopatra butterfly of southern France and Italy, the close relative of our English Brimstone. By waving a grass-green butterfly net in its vicinity I have frequently attracted the yellow and orange coloured males, which will flutter after the net and endeavour to settle on it. The female is similarly coloured to the female Brimstone, but is rather larger. A blue net fails to attract them. G. H. BRYAN.

THE "CRACKING" OF OILS AND ITS COMMERCIAL USE.

ΤΗ HE great consumption of petrol as a motor fuel, which last year, in spite of the disturbing element of war, rose to the enormous volume of 120 million gallons in England, and to nearly ten times that amount in America, has led to the attempt being made to add to the natural supply by the so-called "cracking" of the heavy residual oils left after the petrol and the lamp oil have been distilled off from the crude oil.

The term "cracking" is one of those delightful Americanisms which express so exactly the meaning we wish to impart that it has been adopted universally-when a molecule is decomposed it is broken up when it is merely resolved into simpler compounds it is "cracked." The term first came over with carburetted water gas, when the oils fed into the carburetting chamber were said to be "cracked," i.e., converted into hydrocarbon gases of high illuminating value, but not "broken" into carbon and hydrogen.

A less violent form of the same operation can be utilised to convert the heavy hydrocarbon molecules in oil of high specific gravity and boiling point into volatile liquids fitted for use as a substitute for petrol. Most of the processes for doing this are based on a paper read by Sir Edward Thorpe and John Young before the Royal Society in 1871. This historical memoir was the first and only really scientific attempt to explain the actions that led to an increase in the yield of light hydrocarbons from a heavy oil under certain conditions of distillation, an action that