摘要:

A T the present time there are scores of natural ZA history museums, national, municipal, and semi private, scattered throughout the British Isles, all attempting to serve science by presenting to the people the crude material of scientific study and, less generally, the results of certain kinds of scientific research. Their condition causes uneasiness to the onlooker who realises how potent an instrument museums might be in instilling scientific knowledge and creating that staunch popular backing which is necessary to bring science to its own in the life of the nation. The story of many, perhaps the majority, of provincial museums is the same. They begin in a burst of enthusiasm, the white heat wanes, the care of the collection falls upon a dwindling number of voluntary workers, there is no proper provision for upkeep, and the end is disrepair, mouldy collections, dust-laden shelves-the 'museum' of the comic papers. These museums need encouragement, help, and money. The Carnegie United Kingdom Trustees have decided upon a work of national importance in undertaking, with the help of Sir Henry Miers, an inquiry into the conditions of these " imperfectly organised and to a large extent unappreciated " institutions. The national museums and the museums of the larger municipalities stand in a different category. They are for the most part well tended and well cared for, their exhibited collections are kept up-to-date, in so far as up-to-dateness is satisfied by the replacement of poor specimens, the occasional filling in of blanks and a little more. But have even these museums realised the need of marching with the advance in knowledge?The purpose of a great natural history museum is twofold, as Sir Ray Lankester has pointed out in a recent letter to NATURE (Feb. 26, p. 314). It is a storehouse for the safeguarding of objects of natural history which are of historic interest, and of the vast collections. of specimens gathered from every quarter of the globe and from the world's seas. On these are founded to a large extent our knowledge of the basic natural history of geographical regions, and they afford the raw material for further researches, geographical, morphological, and phylogenetic. Much more importantly, so far as the living generation is concerned, they give the ordered facts on which alone can be based the war against disease, and the search for Nature's wealth, which together determine the economic fate of the human race; but this is an aspect which demands description by specialists. For all these ends the storing of such material, if it is to be at all valuable for reference, demands a minuteness of classification in proportion to the extent of the collections, and therefore a prime duty of a museum staff must be that of the systematic classifier. The other great purpose of the large museum (and almost the sole purpose of the small museum) is exhibitory and educative, for the instruction not only of the unlearned but inquiring public, but also of all grades of receptive mind even to the professional expert, since there is no book-knowledge but may be bettered by reference to the facts themselves, and these could often be displayed from the great stores of museum properties. The growing recognition that an essential duty of museums supported by the public purse is educative, is shown in the placing of the newer State museums under the departments identified with public education, the Victoria and Albert Museum under the Board of Education, the Royal Scottish Museum under the Scottish Education Department. It is a kind of linkage that might well be extended to other public museums, provided the State department concerned is prepared to recognise and develop the enormous teaching potentiality of museums instead of permitting them to adhere as excrescences on the educational body.Have the natural history museums in Britain played up to their educational function ? They have not. Take the Natural History Museum at South Kensington, not because it is worse than the others, but because its size emphasises the defects. Its galleries are for the great part filled with thousands of specimens arranged ' systematically.' The principle underlying systematic natural history is phylogeny, that is to say, systematic collections must be looked upon as illustrating natural relationships and ultimately the evolution of life upon the globe. Since no one can claim that these great collections with their multiplicity of genera and species visibly demonstrate throughout the series natural relationships or the lineage of animal life, their primary purpose fails, and they must be regarded mainly as groupings convenient for showing a conspectus of the animal world and for the identification of specimens. How do the collections meet these needs l It is impossible as a matter of quantity to exhibit every species; it would be useless from a qualitative point of view to do so, for the discrimination of the modern expert seizes upon differences invisible even to the observant eye. But this impossibility makes accurate identification from the exhibited collections a hazardous matter for the non-expert. The collections meet neither the phylogenetic nor the identification point of view. The indication is that their future development must be along the lines of drastic reduction, so that the series shall contain only readily distinguishable forms selected because of their historical, phylogenetic, or morphological interest, or because of a special attractiveness in themselves.The implication of such a reduction is important. It means that, more and more, not only the specialist but also thegeneral inquirer after detailed knowledge must be encouraged to supplement his observations in the galleries by appeal to the cabinet collections. This demands the presence of facilities not at present available in the museum, of easily accessible store collections, of well-lit, well-equipped, reasonably comfortable rooms available for the outside inquirer. Much more it implies such facilities for the museum staff which spends a lifetime organising and sorting the collections in gallery and in cabinet. Hitherto, in this technical aspect of reference collections containing specimens authoritatively named, the British Museum has been the central museum of the world. This position depends largely on the proportion of original specimens, ' type-specimens,' deposited by the naturalists who have named them; and obviously, the museum which has already the widest collection is the museum in which a new type-specimen can be most usefully deposited. It is to examine these type-specimens that naturalists visit England from all over the world. The hidden cabinets form the ' British Museum' which is the premier natural history museum in the world; it remains to be seen whether it can retain this position in face of the intelligent expenditure of America and Germany. Sir Ray Lankester suggests that the exhibition space saved (and he contemplates reduction by one-half) might be used for the purpose of bringing up-to-date this hidden British Museum of research. With this view we disagree. There is a better purpose for the exhibition space, for the Natural History Museum has scarcely touched the fringe of real education, which must become part of the duty of a State museum. The greater American museums have spent much ingenuity and vast sums of money on the creation of realistic Nature groups, which transport the spectator into new realms. The main hall of the Natural History Museum at South Kensington, with its dark alcoves, is admirably adapted for such groups, and might well be given over to this purpose. But while such groups are instructive, their main interest isspectacular, and the public demands more than a pageant: it thirsts for a deeper knowledge. Nearly seventy years ago, Charles Darwin, an Englishman, with a new view-point revolutionised the thought of the world. What has the Natural History Museum of his own country done to make Darwin's world-moving discoveries current amongst his own people ? What has it done to convert the 'fundamentalists,' of whom Great Britain as well as America has its share ? Nothing! Except for a few isolated exhibits, shown almost in holes and corners as if with an apology lest they should intrude upon the systematic collections. Yet Darwin's mind was detailed and material; his theories are not as it were in the air; they rest upon accumulated facts and examples of a kind eminently suitable for exhibition in a museum. Some years ago the late Dr. Benjamin Peach in arranging the collections of Hugh Miller in the Royal Scottish Museum, Edinburgh, placed together a few of the actual specimens which had led the Cromarty stone-mason to certain of his conclusions. This practice might be extended. There is a vast body of general biological truths of vital importance in scientific thought, which could be illustrated, not by one or two examples, but by such a multiplicity of examples, culled from a wide range in the realms of zoology and botany, as would compel belief. Sir Ray Lankester thinks that such subjectsevolution, heredity, variation, natural selection, geographical distribution and variation, sex dimorphism, and hosts of others--should be the subject of museum lectures, and with this view we are in entire agreement; but how much more ought they to fill the galleries of a public museum for the constant reference and edification of the people?Such collections to reach their highest efficiency must be planned and wrought out with a breadth of knowledge, and with a museum gift which is comparable to the creation of a striking and artistic poster; to them each specialist must make his contribution; they must be symposia rather than individual efforts. The hard-pressed specialists on the museum staff, overladen with identification and classification and the sorting of new collections, cannot spare the time and consideration demanded by such biological exhibits. The ideal exhibitor is by nature a creative artist; the British Museum authority, to consult whom a zoologist comes from Japan or a tropical pathologist from Uganda, should be by training a field-naturalist, must be by nature a methodist and a scholiast. The reorganisation of the exhibited collections on the lines of the advancement of modern natural history demands the reorganisation of the staff. On this, as well as on the grounds summarised by Sir Ray Lankester, an inquiry by Royal Commission into the " status, purposes, and organisation of the British Museum (Natural History) and other related institutions " is urgently needed. There are many aspects of museum activities, relationships, and influences which might be bettered by inquiry and definition: the aims of the museum itself; the overlapping and duplication of collections in London; the relation of the State museum as an educator, to the recognised educational and particularly the teaching institutes; its relation to other natural history museums supported by State funds, and to the public museums of Great Britain in general; and not least, when the Dominions, Crown Colonies and dependencies are equipping staffs of researchers into the Nature which surrounds them and the death which encompasses them, who risk their lives to fight disease and to bear the torch of scientific knowledge to the ends of the earth, let the Government of our Empire consider the imperial relationships of the British Museum.

ISSN:0028-0836    

DOI:10.1038/119549a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

BY the " People of the Veil " are meant the 113 Tuareg, whose country extends from the eastern edge of the central Sahara to the far edge of the western deserts of North Africa before the Atlantic zone begins, and from southern Algeria in the north to the Niger and the equatorial belt between the river and Lake Chad in the south. The name 'Tuareg ' is not used by the people themselves; it is really a term of opprobrium originally applied to them by their enemies. They became known to the Arabs as the 'Veiled People,' because their men after reaching a certain age were, as they still are, in the habit of wearing a strip of thin cloth wound around their heads in such a manner as to form a hood over the eyes and a covering over the mouth and nostrils, only a narrow slit being left open for the eyes; and, in default of a national name, they themselves use the same locution in their own tongue to describe the whole society of different castes which compose their community. They are usually included among the Berbers of North Africa; but Mr. Francis Rennell Rodd, the author of the latest book dealing with them, prefers to use the geographical term Libyans, and even doubts whether FIG. 1.-Tuiareg camel-driver. From "' People of the Veil." the Tuareg are Berbers at all, like the other people so called in Algeria and Morocco. There are to-day four principal divisions of them. One of these groups consists of the people inhabiting Air, which is a mountainous oasis situated on a great caravan road from the Mediterranean to central Africa; and it is chiefly with this people and their country that Mr. Rodd's book deals in detail, as a result of a nine months' journey in the Tuareg country. The people of Air have for several centuries had a king, residing in the city of Agades, but he seems never to have enjoyed much authority, unless backed by the more important chiefs. His office is not hereditary, but he is elected by the representatives of certain tribes; and his tenure of office has always been very precarious. The reigning king is of slave descent, and the same has been the case with all his predecessors. The legal practice of slavery has of course been abolished in Air since the advent of the French in the beginning of the present century, but master and slave continue to regard each other by mutual consent in the light of their former relationship. Slavery among the Tuareg never involved great hardship; it was in slave-trading and not in slave-owning that they sinned against the ethical standards which are usually accepted in Europe. There are further the so-called imghad, or serfs, who are clearly the descendants of groups or individuals captured in war and afterwards released from bondage to form a caste enjoying a certain amount of freedom; they are in no sense considered to be the property of the noble tribe which originally possessed them, but the relationship is closer than that of suzerain and vassal. In the first stage the noble tribe represents the original pure Tuareg race, while the oldest imghad are the first extraneous people whom they conquered, " in some cases perhaps as early as in the Neolithic ages."In addition to the social distinction between nobles and serfs, the Tuareg attach great importance to tribal classification. Among the inhabitants of the Air mountains a tribe is either of the category called the " People of the King " or of the Kel Owi, and this distinction means all that the difference between an ancient landed nobility and a parvenu commercial aristocracy denotes. Many of the older men of the " People of the King " say that there are no nobles among the Kel Owi at all. In Air, as elsewhere among the Tuareg, a man's or woman's social status is determined by that of the mother; a woman, they say, carries her children before they are born, and so they belong to her and not to the father. If she marries a man of another tribe the children become members not of his but of her tribe; and Mr. Rodd states that " should inter-tribal hostilities break out they must leave their father and fight for their mother's tribe, even against their own parent if need so be." Similar statements have been made with reference to a few matrilineal peoples in other parts of the world, but they are quite exceptional and even of doubtful accuracy; hence it would have been well if the author had confirmed his asseractual cases in which Tuareg have been with their fathers on account of their mel tracing descent through the mother. He tains that the frequency of monogamy is coi with the 'matriarchate.' But his sta relating to the Tuareg of Air, that in I " monogamy is more frequent than polyga: true of all Muhammadan nations and of ne other peoples who allow polygamy, and has ever been able to show that patrilineal are more addicted to it than matrilineal indeed, the prevalence of mother-right has, contrary, been partly traced to the practicer of polygamy. Monogamy may certainly be a result of the regard in which women are held; but the supposition that their position in general is influenced by the system of reckoning kinship is not past all doubt.Mr. Rodd observes that the Tuareg women are respected by their men in a manner which has no parallel in his experience, and that their unveiled countenances are D in keeping with the perfect freedom they enjoy-though, wisely enc does not attribute the veil worn by the female supremacy. There can be little dou the veiling of women found in many part, Muhammadan world is not merely due to m, jealousy but serves the object of protectin from the evil eye, and in early Arabia ver, some men for the same reason veiled thei particularly at feasts and fairs; but thot belief in the evil eye is known to exist arm Tuareg, it does not seem to have anythinE with the veiling of their men. The author c: some theories as to the origin of this I custom, and is of opinion that up to the no reasonable theory has been advanced. I however, that he has made a little too lighl suggestion that the veil was assumed by who wanted to conceal their faces in oi escape recognition; he argues that the vei be of little use as a means of concealment. I have heard Moors who have come in contact with Tuareg express a very different opinion; and among the mountaineers of northern Morocco robbers blacken their faces so as not to be found out. The veil is not worn until some years have elapsed after the youth begins to carry a sword. While Mr. Rodd gives us much minute and valuable information about the organisation, the social conditions, the mode of life, the trade and occupations, the architecture and art, and the history of the Tuareg of Air, he has much less to tell of their rites and beliefs. Only a few lines are FiG. 2.-Tuareg huts at Auderas. From " People of the Yell." devoted to their customs connected with childbirth, marriage, and death, which may not be so uninteresting as he assumes; and he modestly says that he was not sufficiently fluent in their language to learn much of their superstitions. " Such information," he rightly remarks, " can only be obtained after prolonged residence among a people."He believes that the frequent use of the cross in Tuareg ornamentation is due to early Christian influence. It may be so; but the cross is much older than Christianity, and cruciform devices occur among the tattoo-marks seen on Libyans represented on old Egyptian monuments. It should be added that Mr. Rodd's book is an important contribution not only to our knowledge of the Tuareg, but also to the study of certain problems relating to the history and ethnology of the Sahara and North Africa in general. The illustrations are excellent.

ISSN:0028-0836    

DOI:10.1038/119551a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

PROF. ANDRADE'S well-known introduction to atomic physics has been very largely rewritten for this (the third) edition, and the size of the work has been approximately doubled. Some of the discussions of the earlier editions have been amplified, but in the main the increase in size represents the introduction of new subject matter. As before, the book is divided into two parts, of which the first is nominally devoted to the nucleus. A great deal of extranuclear matter is, however, disposed of in this section, in order to clear the ground for the later discussion of the outlying portions-of the atom. After a brief historical introduction, pride of place is appropriately given to an admirable account of the passage of swift electrified particles through matter-the problem which primarily led to the enthronement of the nuclear theory of the atom. Rutherford's a-particle scattering is naturally dealt with in some detail, together with an outline of the rather less definite evidence obtained from /3particle scattering. There is also a (much too brief) reference to the fundamentally important observations of Ramsauer and others on the behaviour of inert gases towards slow cathode rays-observations now extended, with refined methods, to the more 'aggressive ' gases.Part I. is also distinguished by an excellent account of the remarkable work conducted by Rutherford and his school during the last eight years, on the effects of extremely close collisions between swift a-particles and the nuclei of light atoms-the ' artificial' disintegration of matter and the estimation of the 'size ' of the nucleus. Other topics which are concisely but adequately presented are: positive rays (including Aston's work on isotopes), the evidence for ' energy levels within the nucleus, the interpretation of Aand yray spectra and the deduction therefrom of details of the process of radioactive disintegration. Separate chapters are devoted respectively to more speculative hypotheses on the structure of the nucleus, and to an excellent account of ' classical ' X-ray work-including Moseley's establishment of the importance of the concept of atomic number, Barkla's application of the scattering formula to the determination of the number of extranuclear electrons, and W. L. Bragg's work on the average time-spatial distribution of these electrons. The necessary' Digression' on optical spectra, which has been modified and enlarged, brings Part 1. to a close. Part II., which now occupies about three-fourths of the whole book, deals exclusively with the behaviour of the extranuclear electrons, and almost exclusively with the quantum explanations of this behaviour. A great deal of space is therefore allotted to the discussion of spectral series. This part of the discussion, which has been profoundly modified in the new edition, begins, inevitably, with the classical Bohr theory of the spectra of hydrogen and of ionised helium. This is followed by simplified expositions of Ehrenfest's adiabatic principle and Bohr's correspondence principle. The argument is then carried on to the case of 'hydrogen-like ' atoms, in which two quantum conditions are required for the specification of the orbits, and to the problems of ' relativistic ' fine structure, normal Zeemanand first-order Stark effects. Examples are given of Sommerfeld's classical applications of the 'Sommerfeld-Wilson' quantising rules and of Bohr's use of the method of perturbations. After a preliminary attack on the spectrum of the general atom, with the evocation of selection rules and adoption of a third and fourth quantum number, the discussion of the spectroscopic evidence culminates in a remarkable chapter on multiplet theory and anomalous Zeeman effect. This chapter (xv.), which has been partially revised by Mr. R. H. Fowler, summarises some of the most eminent successes, and at the same time emphasises some of the most significant difficulties and inadequacies of the older quantum theory of line spectra.Among other new chapters which enhance the value of the book, special reference must be made to an excellent summary of work on critical potentials. There is a particularly welcome account of Saha's theory-which is not always, even in astrophysical text books, given the place it merits-and the extensions of Fowler and Milne. Klein and Rosseland's superelastic collisions, and resonance radiation (including quenching and sensitised fluorescence '), are briefly discussed. The account of the evidence from X-ray spectra has been very considerably expanded, and now occupies a separate chapter. This chapter gives a useful account of measurements in ' soft ' X-ray regions and of the transition from optical to X-ray spectra, and a brief discussion of the interesting dilemma of the 'relativity' doublets raised by the recent 'hot spark' work of Millikan and others.The relation of the dynamical atom-model to the periodic system of the elements is much more fully discussed than in the earlier editions. An account is given of the Stoner-Main Smith modification of Bohr's original scheme, and McLennan's new table of basic spectral terms is added in an appendix (v.). The chief addition to the chapter on magnetism is the extended account of the beautiful experiments of Gerlach and Stern, which is supplemented by a particularly fine reproduction of some of the original photographs. There is, however, no discussion of Glaser's work on diamagnetic gases at low pressures.The relative positions of wave theory and classical quantum theory are summarised in a new chapter, which deals with dispersion, the BohrKramers-Slater discussion of radiation fields, and the Compton effect. The book closes with a brief but suggestive statement of the present position, and an account of the salient features of the newer quantum theory -or what seems doomed to be known for the present as the Born-Jordan-Heisenberg-PauliDirac-Schrodinger . . .' mechanics.The above-necessarily imperfect-analysis of the subject matter is intended to indicate the scope of the work, which is in many respects complementary to that of Sommerfeld's well-known treatise. It should be obvious that the book is primarily addressed to the traditional 'serious student' of physics. The treatment is, however, so ordered that much of the text is accessible to readers who have a general rather than a professional interest in modern speculations on the structure of matter. The general plan has been to give a lucid account of the essential features of each problem, and to supplement this by a judicious selection of references to original sources. Space is economised here and there by omitting details for which English readers would naturally turn to such standard treatises as those of the Braggs, Aston, or Siegbahn. The result of this plan has been the production of a book which is specially adapted to serve as a general guide for senior students of physics and for those who are preparing to embark upon independent work. There are also, unfortunately, many older experimenters whose employment leaves them little time to keep in touch with new work which does not bear obviously and directly upon the subjects of their own special studies: to these, too, Andrade's book will make a special appeal.The appeal in many cases will be none the weaker because the treatment is throughout physical rather than mathematical; and although the greater part of the book is necessarily allocated to the theoretical superstructure, unusual attention and respect are paid to the experimental methods and observational data at the foundations. The information has not always been brought completely up-to-date-it is many months since X-ray spectroscopy stopped short at such puny wave-lengths as 14 A.U., and it is no longer held to be established that the absorption edges of an element depend upon the allotropic form, though it has been shown that the effect of valency can be exhibited even in the X-ray emission spectra of compounds-but oversights of this nature are inevitable in so comprehensive a survey. Certain omissions-as that of any discussion of band spectra-were also inevitable, as is pointed out in the author's preface; perhaps one of the most regrettable is the absence of any detailed discussion of the outstanding problem of X-ray absorption. As the problem by its nature is rebellious to direct treatment by the correspondence principle, which is the key to so great a part of the book, this omission is not unnatural.Even if, as the author forecasts, much of the book will need to be rewritten in terms of the new mechanics and the spinning electron, the work in its present form stands as a very valuable exposition of the existing state of our knowledge of atomic structure, and one which is not likely to be superseded in the near future. The advances made even as the book was passing through the press are sufficient to demonstrate the futility of any immediate attempt to assemble, in a work of this kind, more than the barest outlines of the new methods of attack. It is to be hoped, however, that in the next edition it will be possible to include an account of the newer physics which, as yet, is but dimly to be discerned, stirring lightly in the matrices of the new dynamics. The book is well produced, and the new plates are worthy companions to the beautiful reproductions in the earlier editions. The price has been increased-one serious defect in a book which is in all other respects so well adapted to the needs of the experimental physicist-but no one appreciating the amount of new work incorporated in this edition, or familiar with the cost of production of scientific books, will maintain that the increase is unwarranted. There is an excellent index, of the type (combined author and subject) which ought to be made compulsory in all books on physics.

ISSN:0028-0836    

DOI:10.1038/119554a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN his foreword, Mr. Henri Berr emphasises the importance of the social factor in history, and points out that in the early volumes of this series, which deals with the evolution of humanity, it has been necessary repeatedly to refer to the problem to which it gives rise. This volume thus marks a critical point in the general scheme of the series. For here we 'come to grips ' with the problem. The aim of the book is to introduce the social as such into historical explanation. We find, therefore, that it falls into two parts. In the first part, six chapters introduce the reader to what is known of primitive social development, the material being arranged in a progressive framework. After a statement of the problem, it starts with the totemic organisation in which the individual is lost in the totemic group, or, perhaps it might almost be put, the individual is a function of the totem. It then traces the gradual development of individualised power. This is in effect the centralisation of the magic of the totem, of the land and the community, in one individual, the king. In Part 2 the transition of the clan to the kingdom is considered. This is traced in the early civilisation of Egypt and Mesopotamia. Finally, the working out of the social factor is studied in the first empires of the Orient, and the reader is carried down to the Egypto-Hittite entente and the invasion of Egypt by the peoples of the sea in the Nineteenth Dynasty. The application of primitive sociological data to the elucidation of archaological and historical problems is of course not new, but here it is conceived on a grand scale, and worked out in detail with much ingenuity. A word of caution may not be out of place. In this field much is uncertain, at any rate of early days. It is impossible, f or example, to say how great was the extent of the subordination of the individual to the whole. The large generalisations based upon the application of the prevalent analysis to what is often the merest outline, give rise to an uneasy feeling that the interpretation of the more obscure facts has had to square with theory rather than that it has evolved naturally from the facts themselves. In other words, the argument from analogy may have been unduly strained in its application to the internal conditions of Egypt and Mesopotamia.

ISSN:0028-0836    

DOI:10.1038/119556b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

DR. WESTERMARCK'S contribution to the "Forum Series " consists of four chapters in which he follows up the development of the idea of god from its earliest beginnings among primitive peoples in the belief in supernatural beings, to its fully developed form in the higher religions, the religion of the ancient Egyptians, Zoroastrianism, the Vedic religion, Christianity, and Mohammedanism. In the final chapter, " The Betterment of the Gods," the author deals specifically with the ethical side of his theory. The treatment in so small a compass is necessarily concise, and the reader is referred for the data upon which Dr. Westermarck's views are based to his " Origin and Development of the Moral Idea."

ISSN:0028-0836    

DOI:10.1038/119557d0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN a series of experiments now in progress, we are directing a narrow beam of electrons normally against a target cut from a single crystal of nickel, and are measuring the intensity of scattering (number of electrons per unit solid angle with speeds near that of the bombarding electrons) in various directions in front of the target. The experimental arrangement is such that the intensity of scattering can be measured in any latitude from the equator (plane of the target) to within 20° of the pole (incident beam) and in any azimuth.Fee. 1.-Intensity ot electron scattering vs. co-latitude angle for varioue bombarding voltages-azimutb-{111}-33O. The face of the target is cut parallel to a set of {111}-planes of the crystal lattice, and etching by vaporisation has been employed to develop its surface into {11l}-facets. The bombardment covers an area of about 2 mm.2 and is normal to these facets.As viewed along the incident beam the arrangement of atoms in the crystal exhibits a threefold symmetry. Three {100}-normals equally spaced in azimuth emerge from the crystal in latitude 350, and, midway in azimuth between these, three { 1I l}-normals emerge in latitude 200. It will be convenient to refer to the azimuth of any one of the {100}-normals as a {100}azimuth, and to that of any one of the {111}-normals as a {11l}-azimuth. A third set of azimuths must also be specified; this bisects the dihedral angle between adjacent {100}and {1ll}-azimuths and includes a {110}-normal lying in the plane of the target. There are six such azimuths, and any one of these will be referred to as a {110}-azimuth. It follows from considerations of symmetry that if the intensity of scattering exhibits a dependence upon azimuth as we pass from a {100}-azimuth to the next adjacent {11l}-azimuth (600), the same dependence must be exhibited in the reverse order as we continue on through 60° to the next following {100}-azimuth. Dependence on azimuth must be an even function of period 2Yr/3. In general, if bombarding potential and azimuth are fixed and exploration is made in latitude, nothing very striking is observed. The intensity of scattering increases continuously and regularly from zero in the plane of the target to a highest value in co-latitude 20°, the limit of observations. If bombarding potential and co-latitude are fixed and exploration is made in azimuth, a variation in the intensity of scattering of the type to be expected is always observed, but in general this variation is slight, amounting in some cases to not more than a few per cent. of the average intensity. This is the nature of the scattering for bombarding potentials in the range from 15 volts to near 40 volts.At 40 volts a slight hump appears near 600 in the co-latitude curve for azimuth-{l1l}. This hump develops rapidly with increasing voltage into a strong spur, at the same time moving slowly upward toward the incident beam. It attains a maximum intensity in co-latitude 500 for a bombarding potential of 54 volts, then decreases in intensity, and disappears in co-latitude 450 at about 66 volts. The growth and decay of this spur are traced in Fig. 1. A section in azimuth through this spur at its maximum (Fig. 2-Azimuth-3300) shows that it is sharp in azimuth as well as in latitude, and that it forms one of a set of three such spurs, as was to be expected. The width of these spurs both in latitude and in azimuth is almost completely accounted for by the low resolving power of the measuring device. The spurs are due to beamns of scattered electrons which are nearly if not quite as well defined as the primary beam. The minor peaks occurring in the {100}-azimuth are sections of a similar set of spurs that attains its maximum development in co-latitude 440 for a bombarding potential of 65 volts.Thirteen sets of beams similar to the one just described have been discovered in an exploration in the principal azimuths covering a voltage range from 15 volts to 200 volts. The data for these are set down on the left in Table I. (columns 1-4). Small corrections have been applied to the observed co-latitude angles to allow for the variation with angle of the 'background scattering,' and for a small angular displacement of the normal to the facets from the incident beam. If the incident electron beam were replaced by a beam of monochromatic X-rays of adjustable wavelength, very similar phenomena would, of course, be observed. At particular values of wave-length, sets of three or of six diffraction beams would emerge from the incident side of the target. On the right in Table I. (columns 5, 6 and 7) are set down data for the ten sets of X-ray beams of longest wave-length which would occur within the angular range of our observations. Each of these first ten occurs in one of our three principal azimuths.Several points of correlation will be noted between the two sets of data. Two points of difference will also be noted; the co-latitude angles of the electron beams are not those of the X-ray beams, and the three electron beams listed at the end of the Table appear to have no X-ray analogues. The first of these differences is systematic and may be summarised quantitatively in a simple manner. be summarised quantitatively in a simple manner.If the crystal were contracted in the direction of the incident beam by a factor 07, the X-ray beams would be shifted to the smaller colatitude angles 0 (column 8), and would then agree in position fairly well with the observed electron beams-the average difference being 1.70. Associated in this way there is a set of electron beams for each of the first ten sets of X-ray beams occurring in the range of observations, the electron beams for 110 volts alone being unaccounted for. These results are highly suggestive, of course, of the ideas underlying the theory of wave mechanics, and we naturally inquire if the wave-length of the X-ray beam which we thus associate with a beam of electrons is in fact the h/mv of L. de Broglie. The comparison may be made, as it happens, without assuming a particular correspondence between X-ray and electron beams, and without use of the contraction factor. Quite independently of this factor, the wave-lengths of all possible X-ray beams satisfy the optical grating formula nX = d sin 0, where d is the distance between lines or rows of atoms in the surface of the crystalthese lines being normal to the azimuth plane of the beam considered. For azimuths-{ 111} and -{100}, d= 2l5 x 10_s cm. and for azimuth-{110}, d= 124 x 10-8 cm. We apply this formula to the electron beams without regard to the conditions which determine their distribution in co-latitude angle. The correlation obtained by this procedure between wave-length and electron speed v is set down in the last three columns of Table I.TAnLE I. Azimuth.Electron Beams. X-ray Beams.Reflections. AX 10 cm. Co-lat. 8. Co-lat. 8. BmlotCo-lat. 8. Intensity.{ 111100} 54100 174500 3121 050-5 0-91220 {331}{442 2-031-49 113705 44031-6 52-731-6 22-44-36 5947-84 l651.1] 0-770-99 0-91083 17455 015440 1-0170-5 5277-84 1762(0.95) 65126 19044 2920 0-510 l0{311 {422{533 1-84135 1-0459-0 38928-8 43-227g 20-459-0 4-79667 8197-49 1-491-04 0-74188 0980-95 0-832(0.97) 15961 04511} 1-0577-9 {110138 17059 460-07 0-07{420} 531}1-22 1-04785 57159-5 41-76-98 7-751-06 0-891-02 0-95l11} 100{l10 110110 11058 0-15 58 0-1558 0-25 .... ... .... ... - .... .... 623623 6-231-82 1-821-05 1-561-56 0-90Fie. 2.-Intensity of electron scattering vs. azimuth angle-54 volts, co-latitude 50.In considering the computed values of n(Xmv/h), listed in the last column, we should perhaps disregard those for the 110-volt beams at the bottom of the Table, as we have had reason already to regard these beams as in some way anomalous. The values for the other beams do, indeed, show a strong bias toward small integers, quite in agreement with the type of phenomenon suggested by the theory of wave mechanics. These integers, one and two, occur just as predicted upon the basis of the correlation between electron beams and X-ray beams obtained by use of the contraction factor. The systematic character of the departures from integers may be significant. We beve, however, that this results from imperfect alignment of the incident beam, or from other structural deficiencies in the apparatus. The greatest departures are for beams lying near the limit of our co-latitude range. The data for these are the least trustworthy.

ISSN:0028-0836    

DOI:10.1038/119558a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE bicentenary of the death of Newton (March 20, 1727) is within a fortnight of the centenary of the death of Laplace (March 5, 1827), and no one acquainted with the work of both can think of one or other except in association. It may, therefore, not be an unfitting occasion to refer to an historical point with regard to the great Frenchman, when we are celebrating the great Englishman.The physiologist and anatomist Magendie propounded the theory that the intelligence of a human being was in the inverse ratio of the amount of cerebrospinal fluid contained in the brain case. Writing in 1827, the year of Laplace's death, his " M6moire physiologique sur le cerveau," 1 he inserted the following words: "Je me suis trouv6 dans la douloureuse n6cessit6 d'examiner le cerveau d'un homme de g6nie mort dans un age avaneS, mais jouissant encore de la pl6nitude de ses facult6s intellectuelles; la somme totale du liquide e~phalo-spinal ne s'elevait pas a deux onces, et les cavit6s du cerveau en contenaient h peine un gros" [= once]. I have been unable so far to find any further reference in the writings of Magendie " to the brain of this man of genius who died at an advanced age " and in the fullness of his intellectual powers. Magendie appears to have given no further account of this brain; at least I have found none. Laplace died at the age of seventy-eight in the year Magendie wrote. I have also failed to discover any minute record of Laplace's death which would suggest that an autopsy was made or was a " douloureuse n6cessit6." I would venture, therefore, to ask those who may be better acquainted than I am with the circumstances of Laplace's death to let me know why his brain came into Magendie's possession and whether a full report on it was ever written. Magendie, indeed, mentions no name, and this might lead one to consider his investigation of the matter was confidential. However, I think the ascription is certain, for quite recently Miss Helen Hunter Baillie-a lady who combines the blood of other famous anatomists with that of a famous author,2 placed in the hands of Miss Miriam Tildesley a letter of Joanna Baillie to her great niece Miss Sophy Milligan. This letter, dated Hampstead, Monday, 1834, contains the following important paragraph:"MY DEAR SOPHY.... Dr. Somerville told us not long ago a whimsical circumstance regarding the head of La Place, the famous French astronomer. Some Ladies and Gentlemen went one day to the house of Majendie (sic !), the great anatomist, to see the brains of this Philosopher which they conjectured must be of a very ample size, and seeing a preparation on the table answering their expectation they were quite delighted. ' Ah ! see what a superb brain, what organs, what developments! This accounts completely for all the astonishing power of his intellect, etc.' Majendie, who was behind them and overheard all this, stepped quietly forward and said: 'Yes, that is indeed a large brain, but it belonged to a poor Idiot, who when alive scarcely knew his right hand from his left. This, Ladies and Gentlemen' (handing to them a preparation of a remarkably small brain), 'this is the brain of La Place.' Dr. Somerville was told this anecdote by Majendie himself . Your affectionate Aunt, J. BAILLIE." This Dr. Somerville can scarcely be other than the physician, fellow of the Royal Society, and husband of Mary Somerville, the learned lady who studied Newton's " Principia " in the original, was the correspondent of Laplace, and paraphrased his " M6canique Celeste." There can thus be no doubt that Magendie was in possession of the brain of Laplace, and very little doubt that the passage in the " Memoire physielogique sur le cerveau," written 1827, refers to that brain. The questions I would put to the French readers of NATURE are these: What became of Magendie's preparations ? Have they, and with them Laplace's brain, survived until to-day ? If so; has any one reported on it, or does any account by Magendie other than that I have cited, written or printed, exist ? So few brains of great thinkers have been available for examination, that it would be a real disaster if Laplace's should have had only four lines devoted to it.

ISSN:0028-0836    

DOI:10.1038/119560a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WITH regard to the composition of the haze which often obstructs visibility in the summer, the following experiments may be of interest owing to the curious results and the make-shift methods which had to be used.In August last, while staying on the coast of Norfolk, a well-marked haze appeared covering the whole country on Aug. 31 and Sept. 1. This had the characteristic bluish look often seen in summer haze. There was at the same time a strong wind blowing from the sea from north-west by north, which on Sept. 1 veered to nearly due north, the velocity being nearly 20 m.p.h. as measured by the flight of thistledown over a measured distance. The sea was rough, and the haze was such that the limit of visibility was about 5 miles. Having no instruments with me with which to obtain samples of this haze, an instrument was improvised as shown on the sketch (Fig. 1). An empty peach tin 100 mm. diameter had a hole about 2 mm. diameter made in the centre of the bottom. The tin, A, was lashed to a piece of board with string, the bottom being brought up against a step, B, cut on the edge of the board; a microscope slide, C, was fixed opposite the hole in the bottom of the tin by means of a wedge, W, between it and the tin. This wedge also served the purpose of adjusting the distance between the slide and the hole to about 2 mm. The board carrying the tin was attached to a stake about 4 ft. 6 in. high, which was fixed in the ground with the mouth of the tin facing the wind.A clean slide having been placed in position behind the tin, a definite patch became visible in 45 minutes on the glass opposite the hole, where the jet of air produced by the hole struck the slide. It was left in position for a little more than an hour, when the slide was removed and another put in its place which also received a patch visible to the naked eye. These patches, on examination under the microscope, were found to consist of a mixture of drops of liquid and crystals. The first consisted almost entirely of drops when examined, the relative humidity at the time being 82 per cent. On warming gently all the drops dried, leaving crystals mostly of a skeletal form with branches at 90', but some were cubical, while a few were thin rhomboidal plates, and these latter did not deliquesce as the others did when the slide cooled. The second slide was similar, except that there were in the drops larger numbers of rhomboidal crystals which showed no tendency to deliquesce, while on warming the slide numbers of cubical crystals appeared, with sides up to 24 pu, clearly of common salt; also a number of FIG. 1. skeletal crystals with 900 arms (Fig. 2). It would appear, therefore, that this haze consisted almost entirely of crystalline salts, existing partly in the solid and partly in the deliquesced condition, and presumably mainly derived from sea spray, with crystals, probably sulphates, derived from the smoke of cities on the north-east coast. With such a dense supply of hygroscopic crystalline matter in the air it would seem certain that a liquid fog would result from the deliquescence of the crystals present long before saturation, indeed probably in the neighbourhood of 70 per cent. relative humidity.

ISSN:0028-0836    

DOI:10.1038/119561a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

MR. EDWARD MEYRICK, in his comments (NATURE, Mar. 12) upon my paper (Proc. Roy. Soc., B, vol. 101, pp. 115–127) on the egg-laying instincts ofPontania salicis, so completely misses the point that it is difficult to deal with them seriously. The “new principle” to which he refers does not depend in the slightest upon the work he mentions, but is deduced from work described in an earlier paper (Proc. Roy. Soc., B, vol. 99). It may be summed up in two sentences: (1) Chemical agencies acting through ingested food have been shown to act directly on the germ plasm so as to affect its potentialities; (2) Therefore any circumstance bringing about a change in the food ingested by an organism may affect its germ plasm so as to produce heritable variations.Independently of this failure to appreciate the real foundation of the new principle, several other remarks of Mr. Meyrick require criticism. Amongst these is the statement that the only discrimination made by Salix-feeding Lepidoptera is in general between roughand smooth-leaved species, and with this is coupled the remark that the influence determining the choice is touch rather than taste. Such views could not possibly emanate from one who has studied the matter in the field. I have recently been investigating the egg-laying habits of the moth Ypsipetes ruberata, which abounds here in a tangle of Salix pentandra and S. aurita. I can assure Mr. Meyrick that the females, when intent on egg-laying, never approach the S. pentandra to test the roughness of its foliage, but fly directly to the leaves of S. aurita. Moreover, I fail to see how their smoothness or the reverse can affect the choice of food-plant in the case of the lepidopterous Xanthia flavago, the coleopterous Cryptorhynchus lapathi, or the various Cecidomyids of the genus Rhabdophaga, which, with many other species, lepidopterous and otherwise, favour S. aurita in the same thicket but lay their eggs on the bark! The facts are, of course, that the two species of Salix support two very different faunas. Further, Mr. Meyrick cannot really imagine that I' think that the species employed as examples of allied pairs originated in Britain ? I am quite well aware of their range outside our limits, but fail to grasp what this, or the exact locality in which they originated, has to do with the argument. Again, he seems to imply that I consider that a new species has been originated in three generations. No one ever claimed this; the experiments criticised dealt with only one point, that of egg-laying habits. Nevertheless, had Mr. Meyrick understood the principle, or the precise experiments upon which it was based, he would have realised, as is clearly stated in my paper but overlooked by him, that under its workings Selenia bilunaria diverged from the parent stock in wing colour and shape, length of larval life, and other features. These achievements may not, in Mr. Meyrick's eyes, go far to explain speciesformation in the Lepidoptera, but still they do show how breaks from the original species arise which, in the end, may yield new species. One can expect little more in the lifetime of one worker !Mr. Meyrick is correct in saying that entomologists have long noted that groups of related species feed on allied or associated plants and probably arose as phytophagous races. However, recognition of these facts is one thing, and an explanation on an experimental basis is another; this explanation I have endeavoured to supply. As Mr. Meyrick speaks very definitely on the lack of variation, except in size, produced by food amongst the very variable, polyphagous British Caradrinidwe, he doubtless has access to experimental work bearing on the point. If so, these experiments are entirely unknown to me, and should be produced for the guidance of fellow-workers. The only pertinent researches on the Caradrinid~e with which I am acquainted are those of Hasebroek (Zool. Jahrb., Abt. f. allg. Zool. u. Physiol., Bd. 37, 1919), and that investigator gives a very definite correlation between the food and certain phases of variation.In conclusion, I plead for one thing, and that is the removal of the tendency to surround the results of researches in experimental evolution in a cloud of words; what is wanted is not words, but more experiments-and then still

ISSN:0028-0836    

DOI:10.1038/119562a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT seems to me that all the facts of genetics must be accepted so far as they are supported by evidence, but the antagonism of some biologists is, I think, chiefly due to the complacency with which geneticists assume and assert that their discoveries explain all the important phenomena of biology, including the evolution of adaptations. Prof. T. H. Morgan believes that change of structure has been due to mutation, and that organisms have adapted their habits accordingly. I know of no case of mutation which is in any way parallel to the metamorphosis of the flat-fish or the frog.The most crucial test, however, of the claims of genetics is the relation of sex-limited characters to the gonadial hormones. Prof. Morgan's view is that " supposing the testis hormone were the cause of strength and activity in the male which would be preserved and developed by natural selection, their secondary influence over other parts of the body would call for no other explanation." Obviously there is no suggestion here of any reason why the hormone should have a secondary influence over other parts of the body, or what determines the special result of the influence. The antlers of a stag have no essential relation to sex or reproduction at all, any more than its legs. Both legs and antlers are part of its hereditary constitution, but the latter depend for their normal development on the testis hormone, the former do not. Female secondary sexual characters, like the milk glands of mammals, are influenced by ovarian hormones. The only connexion with sex which such organs have is an external one, through function and habits. The antlers are only sexual in the use that is made of them in fighting between rival males. The testis hormone is much the same in all mammals; it is certain that there is nothing in the stag's hormone which would produce antlers in a horse or in a man. Why, then, should organs which have functions related to sexual habits be connected physiologically with the gonads or other reproductive organs ? There is nothing in all the facts of genetics or in the refinements of genetical theory, and nothing known about mutations, which throws light upon the relation of sex-limited characters to the sexual habits on one hand and to the gonads on the other.

ISSN:0028-0836    

DOI:10.1038/119563a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature