摘要:

THE presidential address to thgjwrath African Association for the Advancement of Science, delivered by Prof. HQBfiSintham at SaflisbiVy on June 29, desew^^eej[i|sal b^alliraerestfd In the broader problems of Diolojfy ni its relation to national polity. There are probably few biologists who will regard as unjustified the note of pessimism which makes itself heard here and there in the address: there are equally few who will fail to recognise its common sense and constructive value, or to admit that much of what is addressed to South African listeners is well worthy of attention in Great Britain. Dealing first with the immense spread of education in western Europe and America during the last six or seven decades, Prof. Fantham asks, Has it fulfilled its expectations? This question must be answered in the negative; not, however, that education is itself at fault, but rather that the swarming into the universities of all and sundry in search of a vocational training has brought with it the development of the examination system with its resultant overwhelming of the truly educative by the merely informative function. Initiative, instead of being developed, has been diminished or killed, and the universities, from being the homes of culture and the training-grounds of leadership, have tended to become mere training-colleges for the professions. The universities in turn react upon the schools owing to prospective teachers concentrating their attention upon such subjects as, at the moment, ' pay.' During training in the technique of teaching due attention is paid to drill in the ' principles' of education and psychology, but little to the fact that without solid biological foundations such principles are liable to be no more than the fleeting fads and hypotheses of the day. The teacher is told to ' follow the child ': to make study interesting instead of to make the pupil interested in study. He is unimpressed by the important need to make the child fit into his biological environment by attention to the so-called small things of life-politeness, tidiness, consideration for others, the team spirit, the avoidance of sloppiness-mental, moral, or physical.The instilment of biological principles into the school curriculum means the development of common sense, the appreciation of cause and effect, the development of personal effort, personal observation, personal thinking-all as different as possible from the familiar product of the present day with its absorptiveness of what is served up to it, its responsiveness to popular catchwords and slogans, and its belief in conferences and committees. No section of Prof, Fantham's address is more deserving of serious consideration than that in which he directs his attention to some of the sociological difficulties of the day. He points out the impossible handicap to which the white race is submitting itself by the ever-growing burden of social services with their crowds of officials. Amongst the most costly of these services is school education, but this burden is not incapable of being lightened. ' Frill subjects and snippets ' should be eliminated or paid for by the parent. It is suggested that the education provided free by the State should be restricted to ' the three R's,' the study of the mother tongue-including grammar and composition, the general elements of observational and experimental science, with needlework and cookery for girls, together with a cultural subject, such as singing. Secondary education should not be free-it is a curious human weakness that what is not paid for is not appreciated-but generous help should be available in the way of scholarships to those who are mentally qualified to take full advantage of them.It is perhaps prudent to hesitate before we dismiss all this as old-fashioned, and to ask ourselves seriously whether there is not contained in it a very large infusion of common sense. Prof. Fantham, being a distinguished South African biologist, we naturally turn with special interest to what he has to say on the colour problem, for there are few problems in which attempts to reach a true solution have been more interfered with by the intrusion of sentiment uncontrolled by scientific knowledge. Here we have the opinion of a biologist who realises, as all biologists do, that the black skin of the negro is the outward expression of profound differences of a more obscure kind, which mark him off from the white race as distinctly as does his non-attainment of what we call civilisation, with its complex social organisation, its great cities, its high art, its written language, during all these untold centuries of his undisturbed sojourn in Africa.Prof. Fantham has 110 doubt that the proper line of policy is that of social segregation of the two races. Racial admixture is disastrous in its results. " When once chromosomes of Bantu origin get mingled in white families they cannot be bred out, as is so often popularly supposed, but will exhibit themselves in unfortunate ways and at unfortunate times throughout the ages." What we have to do is to make the black man a, happier and better black man, not to attempt to-make him an imitation white man. He is a country man. He should be settled in the country and trained in practical agriculture, in hygiene and sanitation. He should not be brought into towns and made to do all the manual labour of the whites-with the resultant encouragement of sloth and idleness amongst them. It will be seen that Prof. Fantham's address deals with matters that have been much in the air at the moment. As the columns of NATURE have repeatedly testified during the last few months, the role of science in the school education of the citizen is attracting at the present time much attention and giving rise to much discussion. Not infrequently in the course of such discussion the main issue tends to be obscured through the persistent failure to keep distinct in the mind the two main functions of education-the first in importance, as it is in time, that of educating in the strict sense, of developing to the highest possible extent all these various capacities which combine to produce all-round ability, such as accuracy and rapidity in observation and the accumulation of experience, involving on one hand skill in actual observation, and on the other, skill in drawing rapidly and accurately sound conclusions therefrom; and the second, that of providing the mind with a store of knowledge and culture. Although the boundary between these two functions of education is naturally not a sharp one, it is imperative in order to secure clarity of discussion that its existence should not be ignored.As a matter of fact the educational utility of the two main branches of science-physical on one hand and biological on the other-is related to these two main functions of education. As a discipline for the young child, to develop the powers of observation and of reasoning upon the basis of observation, it would appear unquestionable that it is the physical division of science that is the more useful. By it alone are provided those simple types of observation, capable of exact measurement and of repetition over and over again under approximately the same set of conditions, which arc necessary for the best training in observational accuracy. Moreover, the mathematical methods employed in the treatment of its observations afford a quite unrivalled training in logical reasoning. It is, on the other hand, in the later task of school education, that of turning out the well-informed citizen, that the claims of biology to play an important part are quite irrefutable. In a complex modern State, with its citizens linked together into a biological whole of the greatest complexity, depending for its continued existence upon the applications of biology to food-supply, sanitation, medicine, surgery-its everyday discussions and conversations dealing with subjects like evolution, genetics, birth-control, heredity, public health, and so on-it is clearly absurd that the citizen should not be provided with the foundation of biology without which such discussion is apt to be not merely futile but actually harmful. While probably all qualified by their own experience to form an opinion will be in agreement up to this point, there is unfortunately up to the present no agreed scheme of instruction in elementary biology for schools. The best of such courses as do exist in a few of the great public schools are commonly modelled upon what is required for the first M.B. examination. Even for its own special end-that of providing a sound foundation of scientific biology for the superstructure of the medical curriculum-this type of course is looked at askance by many competent judges, but quite certainly it is not what is required by our ordinary budding citizens. What is required for the education of the general citizen is not a mass of details regarding the ' insides' of men, or rabbits, or crayfish; it is not a collection of packets of ignorance or very incomplete knowledge done up in wrappings of polysyllabic words; it is rather a general knowledge of such of the main developments of biological science as are of importance, either practical or cultural, in the citizenship of the civilised State.Bach of the two main branches, then, of science- the physical and the biological-has its own role to play in elementary education, and it is of the greatest importance to realise this. It is of equal importance to realise what is wanted from each branch. In neither case is it masses of complicated detail. In the case of physical science, it is the careful repetition of observation and experiment in their simplest forms and the recording and treatment of the results arithmetically, the object being to train the young child in accuracy and rapidity of observation and reasoning. In the case of biological science, it is the acquirement of general knowledge regarding main results rather than training in the method of obtaining these results that is required by the citizen. While the physicist may justly claim upon this showing that it is physical science that plays the more fundamental part in the educative process, in actual practice the recognition of this claim has led to strange results, namely, on one hand the denial to biological science of any place in the" school curriculum at all, and on the other, to that hypertrophy of the physical science portion of the curriculum which finds its expression in the schools undertaking courses in chemistry of a standard which is really that of the university. It is a common complaint, as already noticed in NATURE, that students of science and medicine in our universities have to waste an appreciable part of their time at the university in repeating what they have already done at school. The harm is much more than mere waste of time, for the quality of instruction in the average school laboratory is obviously not in a position to claim equality,with that of a university department under the inspiring headship of a leader in his science.When complaint is made of the large and even preponderating part played by science in certain modern developments of our educational system, it is well to bear in mind that ' science ' in this connexion is apt to mean simply physics or chemistry. As stated in NATURE of Aug. 13, of the candidates from grant-aided secondary schools in England in the First School Examination in the year 1926, no less than 40-2 per cent, offered chemistry as a subject but only 2-5 per cent, offered general science. While overwhelming arguments can be adduced for science on the lines above indicated being given an important place in the school training of the average citizen, it is difficult to find any justification at all for bringing him up as a specialist in physics and chemistry completely unversed in science outside their limits. Royal commissions are commonly regarded as the resort of harassed politicians when seeking a means of relieving some inconvenient form of public pressure. But occasionally they achieve great results, and the present would seem a really appropriate time for the appointment of a strong commission to deal with the general question of national education. When such a commission is appointed it is to be hoped that its personnel will consist not of academic specialists, but rather of persons who combine recognised intellectual prestige with understanding and breadth of vision, and that its terms of reference will be as wide as possible so as to include the whole range of education from the elementary school to the university. The selection of the personnel should provide a means of securing that its activities would be confined to big things and not wander away into the desert of detail.

ISSN:0028-0836    

DOI:10.1038/120353a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

RENE ANTOINE EERCHAULT, Seigneur de Reaumur, was born at La Roohelle in 1683. After a short course of training in the law, he devoted himself to the serious study of mathematics, and at the age of twenty-four years was admitted a member of the Academy of Sciences. His life for the next fifty years was one of constant application to scientific research in the departments of physics, metallurgy, crystallography, andmeteoro-logy, as well as natural history. His work included experiments on torsion, on the ductility of metals, on the manufacture of steel, of tin-plate, and of porcelain. In physics he investigated the temperature of mixtures, and devised the scale which long remained the prevailing system of thermometric graduation on the Continent. Reaumur's chief interest, however, lay in natural history, and his achievements both in observation and experiment were truly remarkable. He was the first to describe the ambulacra of starfishes, and to him were due the first systematic observations on the reproduction of cast limbs in the Crustacea, which he attributed to the presence of minute living particles, called by him petits oeufs. The physiology of digestion engaged his attention, and some well-devised experiments enabled him to demonstrate the action of gastric juice upon proteid foodstuffs. But the object towards which his efforts were mainly directed was the study of the instincts, life-history, and general behaviour of insects; and it is on his writings in this department of research that his reputation among present naturalists chiefly rests.The volume before us contains a careful transcription of the hitherto unpublished " Histoire dcs fourmis," which was apparently intended to form part of the seventh volume of Reaumur's'' M^moires pour servir a 1'histoire des insectes," of which six volumes were issued between 1734 and 1742. To the original text, Prof. W. M. Wheeler has added an excellent translation and a series of valuable annotations. In these he has performed the useful task of giving at, length many passages of other authors to which Reaumur refers, and the still more meritorious office of interpreting and correcting Reaumur's statements in the light of present knowledge. It may perhaps be remarked in passing that it would be well if some competent person were to render a like service to the biological treatises of Aristotle. It was scarcely to be expected that the pioneer work even of so shrewd and capable an observer as Reaumur should be free from errors of faulty inference, arising partly from limited opportunities and partly from imperfection of the optical means at his disposal. He was the first to observe the fact that ants ascend trees for the purpose of feeding on exudations furnished by aphides and scale-insects, but it is not surprising that his account contains one or two inaccuracies. So, too, the microscopic technique of his day did not enable him to recognise that the workers were not really sexless, but were normally sterile females. To Reaumur is due what is perhaps the earliest experiment in phototropism. He also was probably, the first to observe recently fecundated females in the act of founding colonies. Gould, to whom the original observation of this proceeding is commonly attributed, did not publish his account until 1747, whereas Reaumur's must have been written (though not published) before 1743. The same remark applies to Reaumur's discovery of the feeding of larvse by liquid disgorged by the workers; also described by Gould in 1747. Another of R6aurmir's records contains the first account of mutual feeding among ants; and yet another, only recently verified, deals with the facilities provided by the workers for the larvse in the act of spinning their cocoons. Experiments were started by him with the object of ascertaining whether ants would tolerate the presence of larvse belonging to an alien community. These experiments, however, apparently did not extend beyond the limits of the same species.In all Reaumur's work, painstaking and thorough as it was, it is curious to recognise that systematic zoology made little or no appeal to him. His interest lay almost entirely in observation and experiment on insect behaviour, scarcely at all in insect morphology. Classification in his day was in its infancy, and we need not be surprised that he draws no distinction between ants and termites. But when we find him saying, " It seems to me that the many hundreds and hundreds of species of gnats and very small moths which exhibit nothing more remarkable than a few slight differences in the form of the wings or the legs, or varieties of coloration or of different patterns of the same colours, may be left confounded with one another," we cannot but realise how widely his point of view differs from that of the modern zoologist. Still more startling, as Prof. Wheeler says, " is his conception of the insects as a natural class, since, like other naturalists of his day, he not only included in it the worms, polyps, mollusks, arachnids, myriopods, and crustaceans, but also the reptiles." The limit is perhaps reached in his remark: " The crocodile is certainly a fierce insect, but I am not in the least disturbed about calling it one." Laxity of this kind was not likely to commend itself to Cuvier, in whose article in the " Biographic universelle," mainly eulogistic, it is possible to discern a certain coolness in regard to Reaumur's merits as a naturalist. Not much sympathy was to be expected between men whose temperaments and methods differed so widely as those of Reaumur and Buffon, and as a matter of fact none existed. There is, however, no sufficient reason for supposing that the non-publifcation of the concluding volumes of the t" Memoires " was due to an intrigue set going by Reaumur's formidable rival.Prof. Wheeler's book is well printed and well produced. It will be of great value to all those who are interested in the historical stages of our acquaintance with the habits and life-history of the remarkable insects of which it treats.

ISSN:0028-0836    

DOI:10.1038/120356a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS volume forms the second of a series of -I- works dealing with the various phases of mining which is being produced by Messrs. Benn, Ltd., under the general editorship of Prof. Henry Louis. To quote the editor's introduction, " There is probably no industry that depends upon so great a variety of other arts and that involves so many branches of science as does mining, nor one that includes such a complexity of operations." The most important of all the phases is the winning and working, or extraction of the deposit. Mineral deposits, broadly speaking, can be divided into two divisions, namely, unstratified and stratified, the former being essentially metalliferous, and the latter largely coal and stratified ironstone and such deposits as the Rand goldfield.The subject of extraction is so wide and varied that the editor of the series has wisely decided to treat it in two volumes, arid this volume deals essentially with the working of unstratified deposits. The remaining volumes of the series are being written by British mining engineers, but the author of this particular volume is a well-known American. As the United States of America is the largest metal-mining country in the world at the present time, the choice of the author is a wise one, as ho has been able to draw upon the accumulated knowledge of his own country to furnish examples and descriptions of the methods of working every conceivable type of deposit. The book is therefore very largely a manual of American practice. There is, in addition, at the end of the book, a short chapter by T. S. Durham describing the methods of working the haematite ores of Cumberland and Furness. The book can be divided into four parts, namely, a general consideration of mining methods and mineral deposits, followed by the three main chapters dealing with narrow, wide, and large ore bodies respectively.The chapter on ore deposits refrains from any comments on the genesis of such deposits, but discusses generally their practical features, such as their varying shape, size, depth, physical characteristics, the effect of the enclosing walls and the behaviour of the surrounding earth masses during and after excavation. In many deposits the line of demarcation between the suitability of open cast and underground methods of working is indefinite. It is quite impossible to lay down any law on the subject, and no attempt is made to do so.The chapter on mining methods is good and comprises two main features; first, a description of the various forms of supports used in underground mining and the conditions under which they may be used advantageously or must of necessity be adopted. The merits of timber supports, the permanent filling of the excavation with waste rock, and the use of broken ore as a temporary support are fully discussed. The second- portion of the chapter deals with the many variations of three simple methods of working which are characterised by the line of advance of the working faces, namely, upwards, downwards, or horizontally. One of these three methods, combined with the materials used for supporting the excavation, constitutes the system of working employed to excavate any given deposit. One of the particular features of this book is the attention paid to the methods employed for working large low-grade deposits upon which the modern mining industry has largely to rely owing to the small comparatively rich deposits of the nineteenth century becoming exhausted. This necessitates the handling of large quantities of material, and many of the methods of working described in detail have been devised for this purpose. When dealing with large quantities small economies make all the difference between profit and loss, and attention is directed to points where saving can be effected.The selection of a mining method is based primarily on its suitability for the physical conditions of the ore body and upon the cost comparison of different methods that may be applicable under the given conditions. Costs are expressed in terms of labour and materials, sometimes graphically and sometimes in tabulated form. This will enable engineers in other parts of the world to compare the working costs of their own mines with those given by the author for alternative methods. In the three chapters dealing specifically with ore bodies of various sizes-a.narrow size being one less than 12 feet thick, while the subdivision of the remainder into wide and large ore bodies allows for a very elastic treatment-the author-discusses the characteristics of such deposits and then proceeds to show how variations in their characteristics affect the method of working. This entails primarily a general statement of the principles involved and is followed up by detailed descriptions of the application of these principles. Many examples of successful application are given, and it is in these chapters that the author's wide experience of American metalliferous mines is displayed at its best.In mining uiistratificd deposits, no general law as to the method of working to be adopted can be laid down. Each individual case has to be decided on its merits, and the decision is further complicated by the uncertainty which always exists as to the size, shape, and future value of the deposit. Knowing this, stress is laid upon the necessity for development work and the provision of ample ' ore in sight.' The numerical value of the ' development ratio ' is not, however, fully discussed. When it is realised that metal mines are being worked at deeper levels every year, and that one of the determining factors in the successful operation of deep, and therefore hot, mines is the comfort of the workers, more space might have been allotted to the necessity for an ample flow of cool dry air round the working faces. The provision of adequate ventilation is intimately bound up with the method of working employed.The book is bulky, being printed on thick paper, and, at the same time, loosely bound. As it should find a place in the library of all metalliferous mining engineers, whose sphere of work is often far from modern means of transport, it might well have been compressed into a smaller and stronger volume. The print is large and easy to read, and the illustrations, many of which have been specially prepared for this volume, are excellent. Tt is the most complete work dealing with the mining of unstratified minerals yet published.

ISSN:0028-0836    

DOI:10.1038/120357a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE author of this volume, himself a doctor of medicine, is inclined to chide the medical profession for neglecting its true patron saint, who was in practice more than two thousand years before either Hippocrates or Galen. It is doubtless-partly to help Imhotep to his own that Dr. Hurry has written the present book. It is, as it could not but be, based on Sethc's masterly memoir on the same subject written twenty-four years ago. There is not much to be added to this-Sethe's work does not age rapidly-but what there is Dr. Hurry has found and added. The most striking additions are the Nechautis Papyrus from Oxy-rhynchus, which, if its story could be trusted, would put back the full deification of Imhotep by 2000 years, Gauthier's article on the Imhotep festival, and Milne's on the graffiti in the Sanatorium of Der cl-Bahri. We are at a loss, however, to understand why he has completely ignored the account of King Zoser given by both the epitomisers of Manetho the Egyptian historian, which, if Sethe's clever and convincing conjecture be correct, is a description of Imhotep himself. Imhotep was an Egyptian Leonardo da Vinci- architect, writer, and physician in one. Though the discoveries at Saqqara during the last two winters have shown that his achievements in building must have been very considerable, it is as a doctor that he survived in the memory of the Egyptians. How soon he became what Dr. Hurry describes as a " medical demigod " we cannot say: probably shortly after his death. In this stage he remained, if we hesitate to accept the evidence of the papyrus mentioned above, until the Persian period, about 525 .B.C., when he first appears with the full attributes of a god. These developments in his status Dr. Hurry describes very clearly and with due regard for the value of various types of evidence. Both here and in the all too short chapter on Egyptian medicine, he shows a happy ability to clothe an ingenious conceit in a neat garb, and this makes his book very readable.A few small points, mostly lying outside the main line of the argument, call for remark. Dr. Hurry has been a little unfortunate in his authorities on some points connected with Egyptian belief. Thus the Liturgy of the Funerary Offerings did not aim at changing the offerings into " a divine and spiritual food, which was partaken of by the souls of the departed" (p. 13). One of the most certain things about Egyptian belief is that the dead were envisaged as still physically living, though perhaps in a slightly different sense from that in which they had lived here. Hence the need for mummification to preserve the body, and the terror lest this should be destroyed. This physical body needed physical food, and that is precisely what was given to it. A similar error appears on p. 64, where Dr. Hurry states that what persists after death is the Jca or double, and that it is this ' part' of a man which needs the nourishment. What eats the food is in reality no ka, but the dead man himself. For such mistakes the Egyptologists and not Dr. Hurry are to blame. On p. 15 we read that the Kheri-heb priest was " by the common people . . . regarded as the mediator between the King and the unseen powers of the universe." Such an idea is totally un-Egyptian. In Egyptian religion the king is in theory the only priest, and the whole funerary ritual is performed by him as the incarnation of Horus for the dead person conceived as Horus's dead father Osiris. There can be no mediator between the king and the gods or the dead. On p. 7.7 we find the curious remark, " More complicated operations were performed on the domestic animals than on man." This is a most interesting example of how errors arise. In the tale of King Khufu and the magician Dedi (Papyrus Westcar) the king wishes to see Dedi perform his vaunted trick of cutting off a head and fastening it on again, and commands a prisoner to be brought for this purpose. The following sentence is obscure, but it would seem that Dedi suggests making his experiment not on a human being but on one of the domestic animals. This I take to be the origin of Dr. Hurry's statement: at least I can find no other.In Appendix B, on the name Imhotep, the author has been dogged by ill luck. The transliteration Ij-m-htp is a purely German form, the German j representing our consonantal y. Read therefore ly-m-htp. Secondly, the verb Titp means not ' to satisfy,' but, intransitively, ' to be content.' Thirdly, there is no ' particle ' m meaning ' as ' or ' in the guise of '; this m is precisely the preposition meaning literally ' in' of which Dr. Hurry has just been speaking. Fourthly, though it is not grammatically impossible that the element ly should be the imperative, yet the rarity of this form and the absence of variants of the name showing the much more common form Mi make it unlikely. In conclusion, I hope that Dr. Hurry's conception of the high standard of Egyptian hygiene is a true one, but I cannot help feeling that if he had excavated, as I have, an Egyptian city, he would have misgivings.

ISSN:0028-0836    

DOI:10.1038/120358a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

OWING to the foresight and initiative of Sir Joseph Hooker, we now possess published floras of many of the British colonies, but such floristic data is only the pioneer work which should form the basis for further research. The time has now come when the investigation of the vegetation of the Empire can be profitably undertaken, and indeed urgently demands attention. Quite apart from the value of such knowledge for its own sake, an ecological survey of the Empire is of paramount importance for its further economic development. To exploit the natural vegetation of any region to the best advantage, we require to know much not only with respect to its existing composition and structure, but also its potentialities under the more or less artificial conditions imposed by man. The British Empire Vegetation Committee appointed by the Imperial Botanical Conference in 1924 in furtherance of these aims has published the volume before us. The first section comprises a brief account of the nature of plant communities, the method of their investigation and the factors of the habitat, whilst the remainder is in the nature of a symposium of essays by different authors which, though often overlapping, have their chief value in the diverse viewpoints which they present, with consequent diversities of technique and emphasis. Moreover, many useful practical hints are furnished for the investigation of the respective areas dealt with. Of especial interest are the sections on the ecology of fungi and lichens by Mr. Ramsbottom.Perusal of these pages emphasises the need in vegetation studies for accurate empirical descriptions unbiassed by any theory which attempts to fit the communities observed into a hypothetical succession series or to find their equivalence with communities in other areas which have been investigated on different lines. Too rigid a uniformity is much to be deprecated, but if the attempts at classification of plant communities are to be rescued from their present somewhat chaotic condition, it is essential that the various aspects of the community and habitat alike should be studied. At present we -know much concerning the soil conditions in the communities of one region, of the putative successions in another, of the physiognomy or the biological relations in a third. Each of these lines of investigation has, indeed, at one time or another, served as the basis of a more or less exclusive classification, but if the pages of this volume serve no other purpose than to bring about a wider and more uniform basis of investigation of the communities within the Empire, the task of the synecologist of the future will be appreciably diminished. How important, from the economic viewpoint, is a knowledge of the plant communities and the successions of any area, is shown by the changes which fire protection has wrought in India, to which Prof. Troup directs attention in his suggestive survey of Indian forest vegetation. Such protection has not only resulted in replacement of grassland by forest, but has also produced profound changes in the composition of the forest itself. The widespread effect of the shifting cultivation practised in the tropics is emphasised by several of the contributors. To this cause both Prof. Troup and Dr. Stamp attribute many of the grassland areas and bamboo thickets in the forest regions of India and Burma, whilst the same factor is held by Dr. Chipp as initially responsible for the forest retreat in West Africa. Prof. Bews shows how a study of the successions in the grass communities of South Africa has both explained the conflicting views respecting the value of burning and supplied the criteria for ensuring the appropriate and successful use of this method.It cannot, however, be too strongly urged that if the fullest use is to be made of ecological methods for the solution of economic problems, it is essential that the study of vegetation should be accompanied by a parallel study of the animal ecology. The valuable conclusions arrived at by Dr. Cockayne in his studies of palatability in the tussock grasslands of New Zealand, have shown how profound an effect the selective action of grazing animals may produce, whilst the thickets of Zizyphus oenoplia in the Central Provinces or the spread of Opuntia inermis in Australia serve but to show that man is not alone in upsetting the balance of Nature to the detriment of his environment.

ISSN:0028-0836    

DOI:10.1038/120359a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE author has collecfe^riarge number of myths and poetical references associated with the heavenly bodies, and^jal woven them into a discursive description or the stars in their constellations and of the members of the solar system. The first ten chapters are replete with legends by which the more spectacular stellar objects (bright stars, double stars, clusters, and nebulse) may be remembered. The remaining seven chapters are descriptive of the sun and its satellite members of the solar system; an interesting perspective of the geological processes through which our planet has passed is given in one of these chapters. Simple language and illustrations £*e employed generally, but a few terms such as ' spectroscope,' ' seconds ' (of arc) might have been explained. A brief description of a refracting and a reflecting telescope is left to the final paragraphs, which contrast unfavourably with the opening sentences of the book. Occasionally accuracy of statement is sacrificed for rhetoric-the sun's corona is described as ' flaming,' and prominences arc spoken of as ' burning gases.' The sentences on p, 12 concerning the measurement of the sun's diameter and those of only four or five of the stars convey a wrong impression of astronomical measurement. A mis-statement appears on p. 74, where the distance of the Andromeda nebula is given as 36,000 light years instead of one million. Incidentally, the quotation on p. 7f>is from Keats, not Longfellow. With slight exception, the reproductions of photographs are admirable and make a very attractive feature of the book;. a few star charts (coloured for preference) showing the whole heavens would, however, have assisted the reader in linking up the many constellation diagrams, a few of which appear somewhat redundant. Finally, it should be remarked that the volume is essentially a gift-book, with its large print, heavy paper, and choice reproductions, and it will be unfortunate if its cost should deter any one from possessing a copy or placing one in the hands of a friend

ISSN:0028-0836    

DOI:10.1038/120360a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

DR. LENZ, as director of the University Crimino-logical Institute of Graz, is well fitted to describe to us the influence of the personality on criminals, and in this book he does this in an extremely able manner. His case material consists of criminals from the prison at Graz and the Petty Assize prisons in Vienna and Graz. He regards crime as the resultant of the interaction of personality and its environment. In the personality he includes the physical structure as well as the psychical, and in this is following much the same lines as Kretch-mer does in his well-known " Korperbau und Charakter." The author divides his book into four parts. The first part deals with his method of investigation and the nature and problems of criminal biology. The second part is concerned with the nature and development of personality, the importance of symbolism and the reaction of the personality to its environment. In the third part, the actual crime and its relation to the personality and its environment are considered. The fourth part deals with the sensory, intellectual, and volitional tendencies, the structure of the ego, and the relation of crime to the sex and herd instincts.

ISSN:0028-0836    

DOI:10.1038/120361b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE ‘singing tube’ has been the subject of a number of short sketches by mo in American scientific journals. There is one form of it, however, that was exhibited at the Cavendish Laboratory in February last that, has never been published, and a brief description of the tube in general and of this special form may be of interest to the readers of NATURE.The singing tube came to my notice quite by accident while blowing a mercury vapour trap for high vacuum work. Two reasons may be assigned as to why it was not discovered long before by research workers doing their own glass-blowing. They are: (a) the trap was blown of Pyrex glass (Moiiax would have answered quite as well), which permitted of more intense heating than soda*glass, and (6) the sequence of operations in blowing happened to be such that it revealed this particular phenomenon. It was soon found that the tube coxild be given the more compact form shown in Fig. 1, drawn approximately to scale. The inner tube (a tost tube) is held in the position shown by three legs fused to the outer wall, and to secure it against mechanical breakage three small supporting nibs (only one is shown) are equally spaced at JV. Roughly, the area of the open end of the inner tube should B*e equal to the annular area between it and the outer tube. The outer tube is closed at M. When the tube is cool, place the tip M in a Bunsen burner flame (as shown in Fig. i) and in a few moments the tube will emit, at its open -end P, a,tone of remarkable purity and loudness. The pitch depends on the length of the tube from O to M to P, this length corresponding approximately to one-quarter of the wave-length of the tone emitted. Extensions attached at P lower the pitch. Two similar' tubes simultaneously heated will sound beats. Many additional beautiful and striking experiments may be performed. FIG.1.FIG.2. The special form of the tube alluded to above is made much longer, and in addition is closed at P, as shown in Fig. 2. On holding this tube in the hands and heating the tip M in a Bunsen flame the operator will feel the tube begin trembling, then violently, and yet no sound is heard. The whole performance is uncanny and one is in danger of dropping the tube. The vibration of the air within will continue for some moments after the tube is removed from the flame. These vibrations may be made audible by placing the closed end P against a resonating body-one's head, a- tin can, a light table, or against a wooden blackboard.The intensity of the tone emitted by these tubes is dependent upon the temperature difference that is established between the tip M and the rest of the tube. The pitch, as previously stated, is determined by the dimensions and is little affected by a change in temperature. It may be of interest to remark that when the body of the tube NOP, Fig. 1, is at room temperature, the tube will begin to sing when the tip is heated to about 400° C. When NOP is cooled to licjuid air temperature, the tube will sing when the tip M is maintained at room temperature, which makes the temperature difference in this instance about 200° C. By extrapolation it was found that the temperature difference required if it were possible to cool NOP to absolute zero would be 80° Kelvin. The pitch of the tone emitted in each of the above examples is correspondingly lowered. The following physical explanation, in collaboration with Dr. Jakob Kunz, University of Illinois, is offered:In the organ pipe, energy is supplied by a stream of air which encourages the vibra-tions in a one-sided way, so that the vibrating column receives an impulse each time when the air moves upward towards the node in the middle of the pipe, Fig. 3. and receives no impulse in the opposite motion. It looks as if a pendulum were kept in oscillation by receiving at one end of its path an impulse always in the same direction. If we were to apply the momentum of the air-jet at the centre of the tube, vibrations of the column would be discouraged. We can communicate momentum to a vertical open-air column by heating it. If we heat the air in the tube in Fig. 4 by a wire net placed in the lower half of the tube, we shall obtain a uniform current of air upwards. If the air is vibrating, then as it is moving inward- its vibration is increased by the momentum of the upward stream of air, but not increased by moving downward. When we place the hot wire net in the middle of the tube it will tend to increase the pressure of the gas when it is a minimum, i.e. it will discourage oscillations. The same will happen when we place the net above the middle. In order to encourage oscillations we have to add momentum in a position and at a moment such that the pressure in the node increases more than it would do on account of the oscillations alone. If we put the hot wire net at the lower end of the tube, i.e. in a loop, the effect will be very small, or zero. The transfer of heat will depend upon the temperature of the air in contact with the wire net, being greatest when the temperature is lowest. But the temperature in the loop at the lower end does not vary; therefore, the transfer of heat in this position of the gauze does not give rise to oscillations. It tends only to raise the temperature of the gas uniformly. Heat must therefore be applied between a loop and a node.If we cover the upper end of the tube, Fig. 5, with the hot net in the most favourable position, the sound ceases, and if we heat by means of a Buiisen burner the outside at the top, as in Fig. 6, we get 110 sound. This was considered by Rayleigh as possible (" Theory of Sound," vol. 2, p. 231). But if we change the cross-section of the tube, as in Fig. 7, and heat at p, then the tube will emit a sound. The pressure in the upper half of the tube will increase, partly because the air is heated, partly because of the condensations of the air in the node on the top. The air will expand, and now the expansion in the narrow neck is aided by the air being heated by the wall. Here the oscillations are encouraged because each time when the air is expanding by the oscillation the expansion is increased by the heat. In each cycle the vibrating particle receives one push in the right direction. It is this one-sidedness of the action which encourages the oscillations. Moreover, as the heat here has the tendency to increase the pressure near the node, the oscillations will start very readily. A slight modification of this experiment is the glassblower's bulb, Fig. 8, which emits a sound when heated around the neck, p. Instead of making the lower part of the tube narrower, as in Fig. 7, we might proceed as in Fig. 9, where the annular area takes the place of the narrow tube in Fig. 8. A modification of this tube is the tube of Fig. 10, which will sound when heated at p and is much more sensitive. It is evident from the explanation that this tube will not sing when the lower end of the inner tube is open, because the one-sidedness of the action is destroyed. Slight modifications of Fig. 10 are the tubes represented in Figs. 11 and 12. If we place a hot wire net inside the tubes of Figs. 7, 8, 9, 10, 11, 12, where the hot flame was outside, the tubes will produce a sound. In all cases, in the organ pipe, in Bijke's experiment (Fig. 4), and in the tubes in Figs. 7-12, the oscillations of a column of air are maintained by a one-sided addition of momentum at the right moment and in the right place. These experiments belong to a large variety of phenomena in which a direct motion is transferred into a periodic motion, or, electrically speaking, where direct current is transformed into alternating c

ISSN:0028-0836    

DOI:10.1038/120362b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT is a well-known fact that when a sinusoidal E.M.F. (of the formE0sin ωt) is available, it is a relatively simple matter to design an electrical system such that alternating currents or potential differences will occur in the system, having a frequency which is a whole multiple of the applied E.M.F.,e.g.2ω, 3ω, etc. For example, when the E.M.F.E0, sin ωtis applied to a diode-rectifier, the current in the anode circuit will include a component of double frequency,i.e.2ω. This is therefore one method of frequency multiplication. Several other methods could easily be mentioned.Now we found it is also possible to design an electrical system such that when the above-mentioned E.M.F., /?" sin ut, is applied to it, currents and potential differences occur in. the system the frequencies of which are, whole subimiltiples of the frequency of the applied E.M.F., e.g. w/2, u/3, u/4 up to u/40, To this end one can make use of the remarkable synchronising properties of relaxation-oscillations 'i.e. oscillations the time period of which is determined by the approximate expression T - irjZ C R, a relaxation time (Balth, van der Pol, " On Relaxation Oscillations," PMl. Mag., p. 978, 1920; also Zeitschr. f. hoc/ifreq. Technik, 29, 114; 1927).Fig. 1. Let Ne in Fig. 1 represent a neon glow lamp, a resistance of the order of a. few megohms, variable condenser of approximately maximum 3500 cm. capacity and E a battery of say 200 volts. In the absence of the E.M.F. E0 sin tat, this system will oscillate with oposoa time period T = a G Tt, where a is a number of the order unity. With the E.M.F. 750sinutf present, where En may be of the order of 10 volts (consider ably lower voltages also give the same result) it is found that the system is only capable of oscillating with discrete frequencies, these being determined by whole submultiples of the applied, frequency. For example, with En - 0, give C a small value such that the natural relaxation frequency of the system is 1000 periods per second. Next period' apply the alternating voltage E0 sin u>i, where w may be made 2 w x 1000 sec."1, then tho system will go on oscillating with a frequency 1000 sec."1. When now the applied Ea sin ut is left as before but C is gradually increased to a much greater value, it will be found that the system continues to oscillate "with a frequency 1000 sec."1. If C is next increased still further, tho frequency of the oscillations in the system (as detected, for example, with a telephone coupled loosely in some way to the system) suddenly drops to 1000/2 sec."1, to maintain this value over a certain range of the capacity value. If G is increased still more, tho frequency suddenly jumps to 1000/3 sec."1, and so on up to 1000/40 sec."1. In some recent experiments it was found possible to obtain a frequency demultipli-cation up to tho ratio 1: 1/200. Often an irregular noise is heard in the telephone receivers before the frequency jumps to the next lower value. TTowever, this is a subsidiary phenomenon, the main effect being tho regular frequency clemultiplicatioii. It may be noted that while the production of harmonics, as with frequency multiplication, furnishes us with tones determining the musical major scale, tho phenomenon of frequency-division renders the musical minor scale audible. In fa,ct, with a properly chosen 'fundamental' w, the turning of the condenser in the region of the third to the sixtii subharmonic strongly reminds one of the tunes of a bagpipe. Fig. 2.In conclusion, we give in Fig. 2 the measured time periods (which are thus found to be a series of discrete siibharmones) as a function of the setting of the condenser C. The dotted line in tho figure gives the frequency with which the system oscillates in the absence of the applied alternating E.M.F. The shaded parts correspond to those settings of the condenser whore an irregular noise is heard. In the actual experiment the resistance R was, for ease of adjustment, replaced by a diode. The experiment, however, succeeds just as well with an ohmic resistance R. Obviously the same experiment succeeds with all systems capable of producing relaxation-oscillations such as described in the papers qu

ISSN:0028-0836    

DOI:10.1038/120363a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT has been suggested to me that I should describe briefly, for the benefit of readers of NATURE who may be interested, some experiments which I showed at the High Tension Conference in Paris a few weeks ago.In January last, as the result of a suggestion by Mr. G. L. Addenbrooke, who had previously investigated the phenomenon, I was able to demonstrate at the annual exhibition of the Physical Society, and again at the Royal Institution, the rise of an oil surface under a charged sphere and the depression under a charged point. As the result of a series of further experiments, it is clear that these first two effects represent two distinct classes of phenomena, namely: (1) The attraction of a high dielectric constant medium through a low dielectric constant medium into the strongest part of the field, and of course the repulsion of a low dielectric constant medium through one of high dielectric constant from the strong to the weak field, and(2) the movement of a fluid dielectric under the influence of a stream of ionised air repelled from an electrode. Fig. 1, a, shows the crateririg of an oil surface under an upper needle-point at about twenty thousand volts alternating. This is effect (2). Air bubbles enter the oil at the point of the crater, but except at quite low voltages they circulate with the mass of oil toward,'} the point.FIG.1. When a thin rod is employed as upper electrode with its end immersed in the oil, the application of the voltage raises the meniscus as is expected from consideration (1) above and shown in Fig. 1, 6. When a certain value of the voltage is attained, however, the oil is thrown down to its ' no voltage ' level accompanied by violent circulation of the oil along the surface away from the electrode. By using in turn a number of electrodes of different diameter and comparing the voltage at which the conditions changed from a steady holding of the oil to the circulation, the calculated stress in the air was found to be the same as previously published values for critical stress in air around cylindrical wires.FIG.2. The electric wind effect is further shown by the repulsion of oil along the surface of a sheet of oiled paper standing on a flat electrode around an upper electrode in contact with the paper.Several effects arising out of consideration (1) above are shown in the remaining figures. Fig. 2, a, shows the attraction of castor oil (d.c. = 4-5) globules in a bath of transformer oil (d.c. = 2-1) into the strong field between two spherical electrodes, with 25 k.v. difference of potential alternating, where they line up. Fig. 2, 6, shows the repulsion of transformer oil globules in a bath of castor oil away from the strong field.In Fig. 3, a, bubbles of air rising through oil between charged spheres are elongated and repelled from the field, while Figs. 3, 6, and 3, c, show the same effects between plates. In the last figure the effect was so strong as to compel the stream of bubbles to avoid the gap entirely. The study of these movements is very much assisted by kinematograph projection, and besides having a close bearing on the operation of cables, transformers, and other plant employing fluid dielectrics, it seems to me that they form a useful means of illustrating the principles involved.FIG.3.

ISSN:0028-0836    

DOI:10.1038/120364a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature