摘要:

ELSEWHERE in this issie we publish the first of a series of brief not on the calendar, which will appe r week in the coming year. T s i deal with hincipa1fasts, feasts, and sti als ofp34s%1 /ear, referring especially to the tra its, the customs, and the usages which are or h been associated with them. When possible, attention will be directed to similar observances in religions other than the Christian where these present analogies to, or serve to throw light upon, the origin and meaning of religious tradition. It is by the citation of such parallels that much in popular belief and custom, which those who in the past were curious in such matters thought merely quaint or inexplicable, has been shown to be a survival of a primitive mode of thought and a corresponding ritual. In his monumental works on early forms of religion, Sir James Frazer has interpreted the meaning of many of these periodic and seasonal observances, and he has interpreted them in such a way as to throw light on their significance in relation to the lowly as well as more highly organised beliefs. Throughout the œGolden Bough, in examples drawn from the beliefs and practices of Christian and pagan alike, there runs the central theme of the doctrine of atonement, of the sacrifice of a deity incarnate in man or animal, of the victim offered up for the salvation of the community, whether it be a community of worshippers or of subjects, andL sometimes of both. Although the more primitive peoples of to-day as we know them may be by no means so unsophisticated as they are held to be in popular belief, yet in the simpler societies the primal springs of action are more readily to be discerned. In the, more complex civilisations of advanced races they are overlaid and obscured by tradition, convention, and sentiment. In all alike, however, from the lowest to the highest, in the ultimate analysis the fundamental urge is directed towards the preservation of the individual and the race. In some cases the two may conflict, as they did in the opposition of the spiritual and the material in the monasticism of the Middle Ages: in extremes both may be ignored. Given these fundamental motives in conjunction with the primitive animistic interpretation of Nature, on one side there arises from the magical ideas connected with the organs of reproduction and their function, an abhorrence of a contraveiition of sexual regulations in combination with.a periodic unrestricted licence of orgiastic rites; on the other, many and various means are brought into operation, especially at certain seasons of the year, to promote the fertility and prosperity of the stock or crops, and to ensure the prservation and increase of the food supply. Th sexual licence of a normally strict society finds its analogy in the sacrificial rite or ceremonial meal which, it hs seen found, at times and with spie,peoples, ignore the taboo of the sacred animal. Nor is it enough thus to enhance actively the forces of Natur the individual and the group must be protected from the influence, more often malign than benignant, of the spirits, whether they be conceived as of the deities or of the dead. Hence the propitiatory rites, the funerary ceremonies, and the various means taken to drive away or ward off spirits and the ghosts of the departed. These dimly survive even to-day. All Hallow-e en is the Feast of the Dead; we still carry the dead man from the house feet first that he may not return.In a community as that of the British Isles, which for the greater part of its history has been predominantly dependent upon agriculture, it should not be unexpected to find customs which point to a survival of these primitive ideas. Many of the customs of the ˜harvest home are to the ordinary observer now meaningless; but when, for example, as the last load is brought in; the men are drenched with water by the women waiting for them, the rainfall which will bring fertility in the future is ensured When in some remoter parts a few stalks of corn are still fastened together in something of the semblance of a human figure or ˜dolly, it recalls the time when the precious seed was preserved for the following season by being regarded as a material form of the deity, and invested with all his sanctity. Tf it were possible to attain a position of complete philosophical detachment, it would not be far-fetched to regard the mystic communion of those who partake of a ritual meal of the first fruits of the grain, which embodies the spirit of the corn, or of the sacrificial victim in the religious rites of some primitive tribe and of those who hold the extreme doctrines of the sacrament as one and the same. To-day in Italy a blend of paganism and Christianity sets up in a field after the harvest has been taken twelve little corn figures around a thirteenth, representing in the traditional form of the corn spirit our Lord and the Twelve Apostles. The election of a King or Lord of Misrule on Twelfth Night goes back far beyond the Saturnalia, with which it is usually compared, to their common origin in the ritual unrestraint of some primitive fertility rite, In even more dramatic form the folk dance ˜gathering peascods ensures magically a full crop by the simulation of gathering it, and the Durham sword dance perpetuates the slaughter of the king to secure in a younger successor the vigour of the community. The Abbots Bromley horned dance may date from an even remoter time when members of a hunting community wore, not ash branches, but antlers on their heads to represent the deer, thus securing the food supply by a ceremonial representation of their prey. The Witches Sabbath, obviously a perverted fertility rite, also may go back beyond the agricultural to a pastoral stage with a six- instead of three-monthly division of the year at spring and autumn, as well as enshrine the memory of a ritual cannibalism not entirely due to a morbid popular imagination.It is not surprising that in the earliest days of the Christian Church a rigid abstention from the rites of paganism was required of believers, an abstention they frequently failed to observe. Civic duties under Roman rule or in a community largely Greek entailed performance of, or participation in, a ceremonial involving religious elements. Further, in aneastern population of mixed races and religions, the desire to take part in a general merry-making is sometimes apt to overshadow differences of belief, The early Christians were forbidden even to join in the custom of an interchange of gifts on the Kalends of January; but how strong was the hold of the old gods is seen in the perpetuation of the Mother Goddess and the Veiled Artemis in the Madonna; the medieval devil still shows the cloven hoof of Pan and the horns of the woodland deities. When the puritanical aloofness of the early Christians gave way in self-defence to a spirit of compromise, the Christian feasts and fasts were made to agree in time with those of paganism or of the old dispensation. The celebration of the birth of Christ was fixed at about the winter solstice, the time of the great feast of the god Mithra, while the Crucifixion and the Resurrection fell at the celebration of the Passover and the spring festival of other oriental religions. It was the duty of the high priest to fix the date of the Passover from observation of the moon s phases: the Church still fixes the date of Easter in relation to the same phenomenon. The coincidence of these festivals did not escape the notice of the ancients themselves, and the followers of Mithra accused the Christians of having copied their rites, while a like accusation was brought against them by the Christians. It must also be remembered that, owing to their racial inheritance and their social environment, the early Christians did not differ essentially in mentality from their fellows. However far apart they stood from them in form of observance and theological doctrine, their fundamental religious ideations had not yet diverged much from those of their contemporaries. Traces of this relationship can be seen in the theological discussions within the Church to quite a late date. Purely mal ideas abound in the writings of the Fathers and the lives of the Saints. Much of medieval and still later belief ”witness the doctrine of witchcraft ”is essentially primitive. Mathew Hopkins, the Essex witch finder, who swam a witch or weighed her against the Parish Bible, differs in method but not in kind from the South African witch doctor who ˜smells out a witch by ˜throwing the bones. Witchcraft was not merely a popular superstition. Even in the seventeenth century, belief in the witch to many was a test of orthodoxy, while the doctrines of the Council of Trent contain elements which are of the purest animism, at least in form, however theological inter pretation may now attempt to explain them away.The reason for the persistence of a primitive mode of thought which we now look upon as alien to the true spirit of Christianity is not far to seek. In the spread of Christianity, however strong the denunciation of paganism, a certain toleration and adaptation was the practice. This was inevitable, especially in the later days of missionary effort, when a prince and all his people might be baptised en masse on one day. It was impossible that every individual, or even that any considerable number, had already been personally convinced of his or her theologicalerror and instructed in Christian doctrine. Consequently, in the remoter parts, such as Britain, Scandinavia, Central Europe, a mass of pagan be liefs and observances survived under the agis of Christianity. Slowly and very gradually, as in succeeding ages an increasing number of individuals of stronger intellectual calibre have emancipated themselves from the trammels of tradition, ritual, and belief has been purged. But in remoter districts, in the Balkans, in Russia, among all the peasant populations of Europe, they linger to-day. In the British Isles most of them have vanished, but here and there traces of a forgotten belief stillremain, while of what is lost something has been recorded by gleaners of these survivals of an older faith. The succession of racial migrations and invasions which the British Isles have witnessed has superimposed culture upon culture. These the archaologist, the ethnologist, and the folklorist seek to recover and differentiate. For this purpose the festivals of the calendar are one of the most fruitful sources. The ritual observances of a primitive people being associated with their chief preoccupation, the conservation of the food supply and the propitiation of the deified forces of Nature, centre around certain crucial seasons of the year, seed time and harvest, the summer and winter solstice, and the spring and autumn equinox. Transformed and degraded, their meaning forgotten, they survive in association with certain dLays and seasons in the Christian calendar. So beneath our Christmas lies the Saxon Yule. A saint s day may hide the festival of a Celtic godd

ISSN:0028-0836    

DOI:10.1038/120941a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE control of water is one of the oldest branches of civil engineering, and to-day problems connected with the flow of fluids are of first importance in connexion with many scientific and technical activities. Like the engineers of ancient times, the modern engineer has to control the flow of water in canals and aqueducts; where they constructed small reservoirs, he constructs tO-day reservoirs of very great capacity. The ancients drew water from shallow wells by primitive means; the engineer to-day uses deep well power- driven pumps to draw water from strata hundreds of feet below the surface of the earth. For thousands of years the power of flowing streams has been utilised to work simple machines, but to-day the rains that fall on the mountain areas are directed into channels that convey the water to machines developing tens of thousands of horse-power. So important has a knowledge of the laws governing the control and flow of fluids become, that in the training of students of nearly all branches of engineering the subject of hydraulics, embracing the fundamental principles of hydrostatics, the flow and measurement of water and other fluids, the design of machines for the pumping of water and for the utilisation of water as a source of energy, form part of the curriculum. It is not surprising, therefore, that there is a growing body of literature dealing with particular branches of the subject, as well as with the fundamental principles of hydraulics. Of the four volumes before us, only the first can be said to meet a real need; the two books on hydraulics contain very little that cannot be found just as clearly and more logically developiIii other books on the subject.(1) Stream gaugig.has become a subject of real significance in the economicie of most countries. The United States, from whih the first book comes, and the Dominion of Canada have for a number of years been engaged in a hydrographic survey of the water available in the natural streams, and very valuable data have been gathered as to the sources of power available, and the water available for irrigation, domestic, and manufacturing purposes. In Great Britain a good deal has been done, but in this country and in other parts of the British Empire much remains to be done, and this work, dealing with American experience, should be useful to students and to engineers concerned in the gathering and utilisation of data. Two preliminary chapters deal with the general principles of the flow of water in open channels in an elementary way, no attempt being made to justify usually accepted formula. In the third chapter, experimental curves (determined by Darcy and other workers) of distribution of velocity in the sections of open channels are considered; the shape of the velocity curve on a vertical section is fully discussed, and methods suggested for finding the mean velocity on a vertical section. Gauging stations and the methods of gauging streams and analysing the results are described in detail. The defectiveness of the current meter in determining small velocities is rightly emphasised, and the student is warned of the care necessary to obtain reasonably accurate results from such instruments. The last chapter of the book deals with a subject not of great importance in Great Britain but of very great importance to Canada; the effects of ice on stream flow and on the form of the velocity curves for ice-covered streams become of very great importance wlieii a stream is required for hydroelectric power production. An appendix is attached of fifty - two well- selected problems relating to the gauging of streams, The work forms a useful addition to the literature of an important engineering and economical subject.(2) and (3) Both the volumes on hydraulics are written for the student. That by Schoder and Dawson claims to have been written, however, ˜ ˜ in the atmosphere of engineering activities. This volume contains matter that is found in other works on hydraulics, but, quite consistently with the real aim of the subject, it only deals with continuous flow, whether in machines or other appliances. No reference is made to the hydraulic press or crane, or to reciprocating hydraulic engines and pumps. The first three chapters deal with hydrostatics and flotation. The flow of fluids through orifices is dealt with in a simple but somewhat empirical manner; there is a lack of logical development and authorities are not quoted. Useful data and references relative to submerged orifices and short tubes arc, howevr, given. The general impression given by the book is that students in the United States approach technical subjects with insufficient mathematical preparation; otherwise it would scarcely be necessary to give detailed instruction as to how the value of v/2g can be obtained by means of a slide rule. The authors appear to be fearful of assuming that readers have an elementary knowledge of the fundamental principles of mechanics, and write a good deal on the flow of fluids before mentioning Bernoulli Âs theorem. On the other hand, the authors plunge into the use of the calculus immediately, in the chapter on flow over weirs, and use it to deduce the flow over a rectangular weir and a V notch in a manner which James Thomson and Prof. Perry years ago thought was entirely unjustifiable. It is an abuse of mathematics to integrate over an area in which the conditions do not even approximate to those assumed in the mathematical analysis. The remaining chapters dealing with flow in pipes and channels and with centrifugal pumps and turbines call for no particular comment. It is of interest to find a chapter dealing with flow of oil and gases in pipes. Reynolds Âs work and the criterion for similarity vd/v is referred to, but this is not developed very far.The book by Lewitt bears much more the stamp of a work specially written with the examination in view, and the whole impression gathered from reading the book is that the least amount of critical study possible has been given to the subject. The only excuse, perhaps a laudable one, is that of dealing with as much as possible in a half-guinea book. As an example ”a very elementary one ” the usual formula v i4/2gff for the velocity of flow through an orifice is given, and two proofs are offered without any reference whatever to the assumptions made. The pressure and direction of motion at the section where the velocity is v is not mentioned, and there seems no escape from the unjustifiable assumption that the velocity v is the velocity through the plane of the orifice; the educational value of a critical study seems to be entirely lost. As another example of the author Âs unjustifiable assumptions likely to be harmful to students, reference might be made to p. 304, on which is given the usual analysis of the formula of Poiseuille to determine the coefficient of viscosity. It then follows that fl = 8()where m is the hydraulic mean depth of a tube and the other terms have their usual significance. Without further discussion he says, œthis may be written V2 \v/ œwhere C and n are constants depending on whether the flow is stream line or turbulent. Such reasoning is entirely unjustifiable, as only by experiment is it, or can it be, known that f(Vd) (vd)fl when the flow is turbulent.So far as it goes the text is clear, and typical examples are worked out, but neither in order or treatment can it be said that the author adds to existing works on the subject. Following other writers, he includes a chapter on presses, cranes, etc. Unless a student knows already something of the constructional details of a single-power jigger, it is doubtful if he will gain much from the illustration on p. 342. (4) The fourth volume, œModern Waterworks Practice, deals very briefly with the fundamental subject matter of the second and third volumes. It naturally commences with œsources of supply. Reference is made to streams, lakes, and underground supplies, and the necessity for careful investigations before deciding upon the water available. The vexed question of compensating water is only briefly mentioned. Earthen, masonry, and reinforre briefly dealt with. The analysis for the buttressed dam may be right or wrong; from the reading of the text it is impossible to say, and the formula given must be taken on trust. The author states that the coefficient of discharge for a syphon spiliway is from 060 to 065, but he gives no authority, and the statement must be taken with great reserve. The descriptions of the various types of plant found in connexion with modern waterworks are clear, though somewhat sketchy, and as a preliminary book for young engineers and students it will be valuable, but for purposes of design, other larger and more critical specialised books will need to be consulted.

ISSN:0028-0836    

DOI:10.1038/120943a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS work, of which the first two volumes have now been published, was planned some fifteen years ago, and was already in active preparation when the European War intervened. When work on it was resumed, the originator and editor, M. Vidal de la Blache, had died, but the project was carried through by M. L. Gallois on the lines that had been laid down. The facts of geography are not new, but the geographer can view them at a fresh angle; and this book is an excellent example f how the geographical outlook, with its selection and correlation of facts and linking of cause and effect, can illuminate the description of a country. (1) Prof. A. IJemangeon, in his volume on the British Isles, has given the best account of the geography of this country that has yet appeared. It is not so full as some regional monographs, but it gains in being more vivid, and the picture of the whole is never dimmed by tedious detail. Not only is he comprehensive in his treatment and accurate in his facts, but also he writes with a clear understanding of the attributes and distinctions of the various parts of the country. We can recall nothing in English that is equally successful in portraying and explaining the scenery of Britain and the life of its people.A book so packed with facts and venturing frequently on estimates of human and social characteristics might well lend itself to easy criticism. But the reverse is true. There is little that one who knows intimately most parts of the British Isles can find fault with. Prof. IJemangeon s cornmand of facts is equalled only by his balanced judgment. Some of his chapters on the landscape and its origin also show great descriptive power. We would commend particularly the chapters on Scothnd, with their intimate study of Edinburgh s traits and his long chapter on London, its origin, growth, and life. One of the few omissions of any significance is an apparent neglect of the port of Immingham, per- haps because its statistics are generally combined with those of Grimsby. Dundee has now no whalers left, and Leith is the only whaling port in Britain. Mentioii iight be made of the part that the granite industry played in the fortunes of Aberdeen. Bibliographies are att3ched to each chapter. On the whole, they are good, even if a few entries might be replaced by more modern books and a few somewhat trivial books omitted. There is a full index of place names. The illustrations are well chosen and are of real value.(2) The second volume, on Belgium and Holland, maintains the same high standard and is particularly interesting in its account of the struggle against the encroachment of the sea and the scheme now in progress for the partial reclamation of the Zuider Zee. The complete work in fifteen volumes is to cover the whole world.

ISSN:0028-0836    

DOI:10.1038/120945a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IMMEDIATELY after the War there was manifested a great enthusiasm for research in nearly all the branches of science, and in agriculture, where the relation of pure science to the applied branches and to the practice of the field is a very close one, there was launched a number of comprehensive schemes both for the pursuit of knowledge and for its dissemination throughout the agricultural community. Thetime has now arrived when it is possible to view the good first fruits of some of these schemes and to say au revoir to others which have been found impracticable, or were born before their time. It is eminently satisfactory to find that so much of the original planning has survived the stringent test of action and that the foundations and footings of a great and progressive agricultural service have been established. This service owes a very great deal to the ability and breadth of view of one man, and as it grows and produces its results, not only in Great Britain but also throughout the British Empire, the great work of Sir Daniel Hall will be made manifest. As chief scientific adviser to the Ministry of Agriculture it has been his business to select from the inchoate mass of suggestions, infer- ences, and wild-cat schemes and to build up a working plan which would cover the needs of fundamental research, agricultural education, and advisory work among farmers, and the terms of the report of the Intelligence Department of the Ministry of Agriculture before us make clear a measure of his success.Such work and such organisation have required the expenditure of very large sums of money, by far the greater part of which has come from the public purse, but, to take a single year as an example, it is reassuring to find that the £700,000 spent in 1925 on agricultural education and research is equivalent oniy to 03 per cent. of the annual production of the land of England and Wales. The research institutes, each with its own department of interest, make possible the carrying through of necessary fundamental work in the increase of knowledge and at the same time give the necessary agricultural bias to the scientific facts evolved. Ideally, they should pursue pure science, with a lively consciousness of the agricultural background which must colour their work in the public view. Actually, they vary very much in their regard for pure and applied science and in their appreciation of the fundamental and ad hoc problems presented to them.One of the great difficulties which has been encountered in the past few years has been the supply of men with two sides to their heads, and capable of appreciating at once both the scientific problems presented in pure research and the bearing which these must have upon practical agriculture. This difficulty has been greater, perhaps, in the recruitment of the advisory services than in the research institutes, but it has been encountered in both spheres, and it has often made difficult the maintenance of understanding and sympathy as between laboratory and field workers. The universities so far have not been entirely successful in producing a supply of research workers who, in addition to possessing a wide view of their subject, are able to think in terms of action. The tendency to strict specialisation in research work is necessarily very great, but there would surely be a great advantage to the agricultural service in general if the young men coming from the universities were compelled to obtain actual field training in some department of an ordinary farm before being allowed to settle down into their allotted groove of work.Students from Scotland and the north of England have a considerable advantage over the southerners, in that a very large number of them have had to work on the land in their early days, and this may perhaps account for the very large percentage of northerners in the research and advisory services. The provision of scholarships, rich enough to attract really able young men of all classes, and the construction of a sort of ladder by which a bright boy can climb from the village school to the greatest of our universities, via such places as farm institutes and agricultural colleges, has helped the supply of men, but there is still much to be done. One of the greatest difficulties encountered in the agriculture of the past has been that of the exchange of ideas between experienced agriculturists and the dissemination of trustworthy information. It is almost proverbial that the link between the laboratory and the farmer is a very weak one, and it is therefore all the more satisfactory to find that the agricultural advisory service continues to grow both in numbers and in the good graces of the farmers themselves.The change in this department in the past twenty years is very remarkable. In 1907 there were scarcely any county organisers and only a few lecturers, and they were regarded with the utmost suspicion by the farmers of their districts. A few outstanding characters earned for themselves reputations for wisdom and soundness, but it was done by force of personality rather than learning. To quote a well- known agricultural adviser addressing a meeting of his colleagues recently: œTwenty years ago no self-respecting farmer would be seen speaking to an organiser; while now they seek you out in the market and, what is more, do what you tell them. There has been a great change of heart, and the present generation of farmers i anxious to learn, and is not convinced that the law of the grandfathers is immutable. The organisation of the framework of the advisory system is almost complete over the country, and the supply of trustworthy information to farmers on almost every subject connected with their business is assured. It remains now for the advisers themselves and the farmers to take full advantage of the inquiring spirit of the age and of the opportunity which is offered. We, especially those of us who are farmers, have been apt to regard our own coasts as the limit of our concern and interest. This parochial view is shaken daily by the closer contacts in the market and in conclave with other parts of the British Empire, and it is interesting to find that our home advisory service is being depleted of some of its best young men by the creation of attractive posts for them overseas. An Empire Marketing Board, an Imperial Research Conference, a commonpool of researeh workers and advisers ”it seems that agricultural science pro- gressive and well organise(I is about to take its proper place as one of the dominating influences in the development and progress of the Empi

ISSN:0028-0836    

DOI:10.1038/120946a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

A COMPLETE history of the forests of Belgium from the earliest times up to the end of the eighteenth century is given in these three volumes, which embody the results of much learned research. The economic and social importance of the forests throughout the ages is the main subject of the work, but much light is also thrown on the natural history of the woodlands and on the gradual but late development of scientific sylviculture and forest management. Folk-lore, legislation, charters, archives, ancient MSS., classical writings, and modern books have all been laid under contribution. An agreeable feature of the work is the high quality of the full-page illustrations, which reproduce famous landscapeS pictures, maps, plans, and photographs. A great variety of information, is scattered throughout the work. In every period much destruction of the original forests has taken place. The early natives and their Roman masters regarded the forests as inexhaustible, and ruthlessly plundered them for fuel and timber. Increasing population necessitated more agriculture for its support, and this was only to be obtained by encroachment on the land covered with trees. From the sixth century onwards, the civilising Benedictine monks, in their zeal for farming, were probably more destructive of woodland than the early pagans. The forests that now exist in Belgium and France owe their preservation throughout the Middle Ages to the feudal lords, who loved the chase, and instituted severe game laws, (lepriving the peasants of their rights to fell timber and pasture their flocks in the forests. The si es of the ruined forests can often be recognised in the modern names of villages and communes. Ypres was so called on account of the elms (yppen in Flemish) which were numerous in the woodland where the town was first built. In the years before the War, the country around Ypres was still noted for its numerous fine elms, which were survivors and descendants of the trees in the original virgin forest.

ISSN:0028-0836    

DOI:10.1038/120947a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN this booklet, Dr. Arnold Sack, of Heidelberg, has made a judicious selection of the most important passages in the works of Hippocrates and rendered them into readable German. The passages selected include the oath, and extracts among others from the law, the surgery, the epidemics, airs, waters, and places, the prognostics, dentition of infants, nature of man, care of health, and numerous aphorisms. In the postscript, Dr. Sack maintains that though nothing definite is known about the life of Hippo- crates, it is certain that he was not a mythical personage, but really did exist, as is shown by allusions to him in Plato s dialogues, and not only practised medicine but also wrote medical works. It was not until many centuries after his time that commentators of the Hippocratic works appeared in Alexandria, Athens, and Rome, the most pro- niinent of whom were Galen and Herophilus. No critic has yet been able to determine with certainty which of these works was written by Hippocrates himself and which by his pupils. It is, therefore, not surprising that some of the passa es selected by Dr. Sack are from works regard y other commentators as spurious.

ISSN:0028-0836    

DOI:10.1038/120948c0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WE have read the reply of Messrs. Reid Moir and Burchell, published in NATURE of Nov. 26, to our letter on the above subject. We note that we or our observations are old-fashioned, unwise, faulty, mistaken, abortive, dogmatic, and so forth; but we find little or no serious attempt to meet the main points of our criticisms, and we are so “unscientific” as to hold that detraction is not argument.Messrs. Reid Moir and Burchell specified three sites as sources of their ˜implements. They admit by implication that we identified two of these; for they make no effort to question any of our statements regarding them. The third, they suggest, we œfailed to observe. This is not the case; and their suggestion, based as it is upon an ambiguity of topographical nomenclature, is scarcely ingenuous. The square- headed promontory of carboniferous limestone, south of lJrumcliff Bay, comprises the townlands of Upper and Lower Rosses. In some of the older maps only the north-western angle of the pomontory is called Rosses Point: but in curreit modern usage this iiame has been extended far beyond that narrow application, to which Messrs. Reid Moir and Burchell now wish to confine it. The village, church, post-office, hotels, etc., of Rosses Point all lie along the south coast of the promontory, one to two miles distant from the north western angle. Those unacquainted with the district can verify this by reference to any recent map, such as the six- or one-inch Ordnance, Bartholomew s quarter-inch, the Admiralty Chart, etc. Knowing this, and assuming that Mr. Burchell also knew it ”as we think he must have done ”we covered with our survey the œwestern or seaward side œ of the whole promontory, including the north-western angle; with the results stated in our first letter. We have there already mentioned the only features, along the strip of coast in question, to which the term ˜rock-shelter, fallen-in or not, could by any stretch of imagination be applied; or to which Mr. Burchell s ambiguous indications could in reason be referred. At this north-western angle, where we now learn definitely that Mr. Burchell s ˜rock-shelter is situated, we found only an ordinary storm-beach, composed of angular blocks derived from the rocks around it; and limited, as to its dimensions, by the nature of the ground, the character of the rocks, and the manner of their erosion. As there can now be no doubt that this is what Mr. Burchell claims to be a fallen-in rock-shelter, it becomes necessary to describe it with some particularity.The beds of limestone referred to dip at a low angle towards the north-west. At the spot where the ˜rock-shelter is situated three beds are present. The upper, evidently the ˜roof of the ˜rock-shelter, is formed of a very cherty, much jointed grey limestone, and is about 2 feet thick. The middle, which is about 4 feet thick, consists of more thinly bedded grey limestone, almost devoid of chert. The lower, the ˜floor of the ˜shelter, is a more massive and compact limestone, brownish on the surface, quite devoid of chert, and easily distinguished from the other two. The middle bed yields to marine erosion a little more rapidly than either of the others. In consequence, undercutting of the upper bed is continually in progress; but, owing to its strong jointing, blocks fall away from it before there is any marked over- hang. For this reason it is impossible that it could ever have formed a roof capable of giving shelter. The erosion of the middle bed exposes the lower bed, and from this latter rather large blocks, sometimes as much as three or four feet in length, become detached from time to time, and are cast up to a higher level by the winter waves. The erosion of the three beds thus advances, to all intents and purposes, con- currently.The resulting storm-beach covers the whole area of the alleged ˜ rock-shelter ˜; and its dimensions agree with those of the ˜ shelter, as given by Mr. Burchell. But of the blocks which compose it, only about one- third come from the cherty upper bed (the ˜ roof ˜) the other two-thirds come mainly from the lower bed (the ˜ floor .), having been cast up by the waves to a height several feet above their original position, so that they overlie some of the smaller debris. The middle bed breaks up more readily into small pieces, with angular fractures. Many of these fragments are so recently broken that they have not yet been rolled by the waves, though some of them display chipped edges, produced by marine action. Storm- waves have free access to this material, as is shown by the copious admixture of recent marine shells associated with it ”some of the bivalves being so fresh that they still retain their ligament. This mixture of stones and shells lies around and beneath the larger blocks; and it is from this material that Mr. Burchell s ˜implements have been selected.The suggestion that this mass of rock debris could have formed the roof and contents of a Palieolithic rock-shelter would have appeared to us so ludicrous, had it so much as occurred to us, that we should have dismissed it forthwith. Since the publication of Messrs. Moir and Burchell s most recent letter, definitely indicating this spot as the site of their rock- shelter, two of us have revisited the place and reexamined it with care. Their report confirms us in our former conclusion ”that it presents nothing more than a typical storm-beach, similar to those that are to be seen on Coney Island and at other places in the neighbourhood. After this second, more thorough examination, we are now able to say that in spite of Mr. Burchell s depredations it would still be possible to select, from among these fragments, specimens presenting a very passable resemblance to implements. There would be no difficulty also in finding among them shapeless lumps of stone which the most sanguine could never mistake for artificial products. If these two groups were laid out at a short distance apart, we might, with no very great expenditure of time and trouble, fill in the space between them with a complete seriation of forms, gradually approximating from the one to the other. Even without the advantage of seeing Mr. Burchell s carefully chosen specimens, we can well believe that they look very convincing on the table of the Society of Antiquaries: but we suspect that they would be less impressive if they were lying where the last storms left them, mingled with these countless intermediate forms and with modern seashells.Mr. Burchell s œRaised Beach of powdered shells can be readily seen in the earthy bank just behind his ˜rock-shelter, though his reason for calling it ˜Early Neolithic is less obvious. It is a mere upward extension of the recent beach, and is likewise due to storm action, probably within the last century or two. The lighter fragments have been projected by spray and wind farther than the heavier ones ”that is the only difference which this upper edge of the beach presents in contrast to the lower part. The shells are of species now common in the bay, including S olen siiiqua (predominating), Venus gallina, Cardiam edule, Donax vittatus, Mytilus edulis, Ostrea edujis; they occur in the same relative pro- portion from the highest point of the so-called ˜ raised beach ˜ down to the lowest point of the present beach. By quoting in support of their case a reference from the GeologicalSurvey Memoir to a raised beach at Carney, Messrs. Moir and Burchell show themselves to be unaware that the study of Irish raised beaches has progressed within the forty years which have elapsed since that memoir was published. The Carney ˜ raised beach ˜ is wrongly so described; it consists of shelly deposits, due either to recent storm action or to human agency. Similar shelly beds are frequent along the Irish west coast, as in Counties Mayo, Gaiway, and Clare. Those of human origin date, some from the famine year (1847), some earlier, some later. The well-known 25-ft. beach of Northern Ireland, so conspicuous in the north-east, drops to sea-level and merges with the present beach in Co. Wicklow in the east, and Co. Sligo in the west, as is well shown . 422, Fig. 151. We repeat; No raised beach is known within this area. If they had realised it, we were doing Messrs. Moir and Burchell a service in pointing out their error in this matter. For, under the conditions prevailing on this spot, a Neolithic raised beach overlying a Paheolithic rock-shelter, such as Mr. Burchell describes, would be damning evidence against his claims. We invite a consideration of what it would involve. (1) A rock-shelter formed by marine action in strongly jointed and bedded limestone, on very exposed ground, with (2) Mousterian implements on its floor; (3) heavy glacial erosion of the district; (4) submergence, until a beach was deposited above its roof; (5) emergence, until its floor was a few feet above ordinary high-water mark; (6) recent coastal erosion, postulating more rapid erosion during the two preceding phases; and (7) after all these vicissitudes, the rock-shelter still surviving, save for blocks fallen from the roof, and still retaining exposed on its floor œmore than 100 unrolled flakes and flake implements made of limestone (The italics are ours.)Messrs. Reid Moir and Burchell complain that we prejudged the authenticity of the material removed to London without having examined it. If they will refer to our previous letter they will see that we were careful to avoid doing this. They also charge us with a desire to maintain at all costs a preconceived theory of the absence of Palaolithic remains from Ireland. Personalities of this kind possess neither interest nor importance, and are best ignored; but we may permit ourselves to say that here also they make a statement contrary to fact. We are ready to welcome any discovery of Palaolithic man in Ireland, by whomsoever made. We visited Rosses Point with perfectly open minds. Had we found that the sites agreed with Mr. Burchehl s description, we should naturally have endeavoured to follow up our inspection of the ground with an examination of his collection. But the geological evidence proved so destructive that we considered that no useful purpose would be served by a journey to London, until the difficulties presented by the nature of the sites had been cleared up. This, we repeat, Messrs. Moir and Burchell have made no serious effort to do: accordingly our case rests where it did. Much more might be said on other points that have been raised in this correspondence: but we do not propose to trespass further on the hospitable columns of NATURE, unless some new statement of fact be made, which in our opinion calls for notice. Just as a sentence removed from its context can convey a surprisingly false impression, so the Sligo ˜ pakeoliths, brought to notice by Messrs. Reid Moir and Burchell, cannot be fairly and fully judged without a competent study of the sites that yielded the

ISSN:0028-0836    

DOI:10.1038/120949a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

PROF. A. H. COMPTON's own explanation of the remarkable phenomenon discovered by him is well known and is set out very clearly in his recent book on “X-rays and Electrons.” Briefly, it is that radiation is of a corpuscular nature, that the momentum of the impinging quantum detaches the electron from the atom and causes it to recoil, while the deviated quantum loses energy in the process and degrades in frequency. This view of the Compton effect, like Einstein's explanation of the emission of photo-electrons, approaches the relations between matter and radiation from a point of view so divergent from that of the familiar concepts of Maxwellian electro-dynamics, that it is scarcely possible to understand how this conception of radiation is physically reconcilable with the familiar explanations of interference and diffraction phenomena.As is well known, there is an addition to the X-ray scattering of degraded frequency, an unmodified secondary radiation the existence of which has been explained by Prof. Compton as due to the whole group of electrons in the atom scattering conjointly. To this view, the objection might be raised that if one electron acting alone can scatter a quantum, and also all the Z electrons in the atom acting together, then why do we not observe scattering by two, three, or more electrons acting together at a time, with their corresponding fractional Compton shifts in wavelength ? To the alternative explanation of the unmodified scattering given by Profs, Compton and Jauncey that it represents the scattering by an electron which the impinging quantum is unable to detach from the atom, the equally pertinent query may be asked, then why is the intensity of this type of radiation proportional to Z2 and not to Z? In addition to these objections to Prof. Compton s explanations of his own discovery, there is another of a very fundamental nature which was also urged by me when, by invitation, I spoke at the British Assoelation meeting at Toronto in August 1924, on the problems of the scattering of radiation. Maxwell s theory of light not only explains the classical phenomena of interference and diffraction, but also, when taken in conjnction with the principles of thermodynamics, affords a very complete explanation of the phenomena of the scattering of ordinary light in gases, liquids, and crystals under the widest range of physical conditions. This has been fully demonstrated by me and my associates in a series of experimental and theoretical researches during the last six years. Is it conceivable, then, that Maxwell s theory and thermodynamics taken together would fail in the closely allied field of X-ray research ? Urging this point of view, I referred at the Toronto meeting to the beautifully simple explanation which the classical wave-theory and thermodynamics together give of the X-ray diffraction haloes in liquids.Durin.,the current year I have returned to this subject, and in a series of memoirs which are being published in the Indian Journal of Physics, have developed a general theory of X-ray diffraction and scattering in which thermodynamics, the classical wave-principles and modern views of atomic structure are brought together and shown to afford a simple and intelligible explanation, not only of Prof. Compton s own discovery, but also of the crucial experiments of Bothe and Geiger, and of Compton and Simon, which at first sight seem so destructive of the classical wave-ideas. It is not possible in the columns of NATURE to afford more than the briefest indication of the line of thought followed in these memoirs. The facts of temperature radiation from solids and fluids compel us to assume that the thermal agitation of bodies excites not only the atoms but also the electrons contained in them. Starting from this premise, it is shown on Maxwellian wave-principles that we must have two types of secondary X-radiation, one of intensity proportional to Z2 which corresponds to the normal or stationary state of the atom, and the other proportional to Z produced by the thermal fluctuations of the internal structure of the atom. The former is a stationary or diffrac-tion effect, and the latter is of a highly fluctuating type, the intensity of which has no fixed values at any time or place and the laws of which can only be formulated as statistical relationships. This type of scattering is identifiable with the Compton effect, and the observed variations of the latter with direction of observation, atomic weight of scattering atoms and wave-length of X-rays, and the observed fluctuations with respect to time and direction, are all satisfactorily explained.In addition to these, the theory indicates that as the Compton effect is essentially a thermodynamic phenomenon involving degradation of energy, it should show a marked dependence on temperature. Experiments to verify this are in progress at Calcutta, but there are already sufficient indications in the literature of X-ray scattering and absorption and their variations with temperature to indicate that the success of the experiments is a foregone conclusion. The results of the experimental work will also be published in the Indian Journal of Phys

ISSN:0028-0836    

DOI:10.1038/120950a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

LAST year Dr. Honda and the present writers published a paper dealing with the magnetic properties of single crystals of iron (NATURE,117, 753; 1926). The present paper contains the result of the similar investigations on nickel. In order to obtain large crystals of nickel, a strained bar of electrolytic nickel meltedin vacuowas continuously heated at 1300° C. for several days, but the result was the formation of twinning crystals of several millimetres in length and no further growth took place. In the second trial, molten metal was cooled from the bottom of the crucible containing it by slowly lowering the vessel out of an electric furnace; in this way we were able to prepare large crystals of nickel, 7 cm. in length and 2.3 cm. in diameter.From these crystals three oblate ellipsoids, the flat planes of which coincided respectively with three principal planes (100), (110), and (111), were prepared. The major axes of the ellipsoids were about 20 mm. and the minor axes 06 mm. The processes of sawing and filing were always done by hand very carefully so as to avoid the least distortion of the crystal. The results of the measurement of the magnetisation in the direction of the principal axes of the crystal are shown in Fig. 1. As is seen in the figure, the magnetisation curves in the directions of the tetragonal, digonal, and trigonal axes are almost straight, and coincide with each other up to an intensity of magnetisation of 205. Above this intensity the magnetisation varies for the different axes of the crystal, the trigonal, digonal, and tetragonal axes showing a decreasing order of magnetisability. This is just the reverse of the case of iron crystal. The saturation intensity of magnetisation is 503, which is higher by 5 per cent. than the value 478 obtained by P. Weiss, and lower by 1 per cent. than the vahie 509 determined by E. Gumlich.In plane (100), both parallel and perpendicular components of magnetisation in a constant field vary with a period of 90 °. For the parallel component, the direction of the digonal axis has the maximum magnetisation, and that of the tetragonal axis the minimum magnetisation; but for the perpendicular component, the magnetisation vanishes in the direction of the tetragonal and digonal axes and attains a maximum or minimum between them. When the intensity of the magnetic field increases, the amplitude of these periodic changes increases, attains a maximum, and afterwards gradually decreases. The above periodic change coincides qualitatively with the case of iron crystal, when the direction of its principal axis is supposed to be rotated by 45 °; this difference may be expected from that of the lattices in (100) plane for iron and nickel crystals. In plane (110), two components of magnetisation vary with a period of 180 °. For the parallel component, the principal and secondary minima take place respectively in the directions of the tetragonal and digonal axes, and the maximum in the direction of the trigonal axis.In plane (111), the two components of magnetisation vary with a period of 600. The amplitude of these periodic changes is very small, not exceeding 4, which is only 4 per cent. of the maximum amplitude in the plane (110). In a weak field, the parallel component of magnetisation in the direction of the side of the equilateral triangle forming the space- lattice is a minimum, and that in the direction of the bisectors of the vertical angle of the triangle is a maximum; but in a stronger field the opposite is the case. These relations coincide qualitatively with the case of the (111) plane in the iron crystal when the direction of the principal axis is rotated through 30°. The magnetic expansion ”field curves for the directions of tetragonal, trigonal, and digonal axes are shown in Fig. 2. In the case of the longitudinal effect, magnetic contraction is observable for all fields, while in the case of the transverse effect, magnetic expansion is always observable. In both cases tetragonal, digonal, and trigonal axes are in the descending order for magnetic expansion or contraction; thus the order is just the reverse of the magnetisab

ISSN:0028-0836    

DOI:10.1038/120951a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN the article on radio-frequency measurements in Glazebrook's “Dictionary of Applied Physics” (vol. 2, p. 635), Dye states that “quite powerful longitudinal vibrations in steel bars can be produced by acting on them with currents of the resonating frequency.” From conversation with Dr. Dye, I gather that this refers to some otherwise unpublished work in which the oscillations are maintained by electric, that is, electrostatic, forces derived from an oscillating valve set and a polarising battery.Experiments made by me on audio-frequency oscillations of metal rods under electric forces from a valve show that these vibrations can be obtained of great intensity with surprising readiness. The metal bar (of cast steel, mild steel, or brass) is clamped at its centre, and one plane end is placed close to the plane surface of a massive block of metal, This block and the bar are connected one to each side of the condenser of the valve maintained circuit, a polarising battery being inserted in one of these leads. Tuning is carried out at first by comparing the note emitted by the bar when struck endwise with that heard in the ear-piece of a reed telephone, to which no leads need be attached, since the stray magnetic field from the induction coil in the valve set makes it give out a note of the frequency of the set. The final tuning may be made in this way by beats, or by beats between the forced oscillations of the bar and its natural oscillations evoked by impact. A bar of the same material of half the length will vibrate without the polarising battery if the condenser in the maintaining valve set be cut down to a quarter of its former capacity. The fine tuning in this case is by beats between the natural note of the bar and a faint note emitted by the induction coil of the set. This note is due to the unpolarised vibration of the structure of the coil set up by the main oscillating current. Rods and tubes of electrically non - conducting material could doubtless be caused to oscillate in both these ways, that is, by polarised or unpolarised electromagnetic forces, by winding them suit- ably with conductors. Non-conducting rods could also be used for the electric attraction method after rendering one end conducting and providing a conducting path from this end to the clamp by plating or otherwise. The advantages of fused quartz for such work are patent.Magneto-striction is a unidirectional effect in nickel. In iron and steel the effect is less, and in some circumstances does not increase with increase in field. There appeared then the possibility that attempts to maintain oscillations by magneto-strictive forces might fail with iron and its varieties, but succeed with nickel. Troubles threatened to arise in consequence of eddy currents and hysteresis. However, it turned out on trial that cast steel bars and mild steel bars could be maintained in resonant vibration with very great facility. With nickel the effects are even more striking. Both polarised and unpolarised electrostri.ctive forces may be employed. In the polarised case a coil carrying a constant current surrounds the middle of the bar, and the oscillating current from a valve set is sent round a coil conveniently wound on the same former. To obtain the unpolarised effect, care should be taken that the bar is not magnetised to begin with. If it is magnetised one can very readily obtain the polarised effect; the permanent magnetic state of the bar then performs the function of the direct current. If the induction coil of a ˜tuned anode assemblage with grid coil coupling be itself used to provide the alternating field, then it is convenient to provide a separate winding for the direct current. In this case a galvanometer in the grid coil will indicate the presence of the oscillating bar. The variations in the defiexions of the grid galvanometer are similar to those in which the set is influenced by a neighbouring resonating circuit, a result in accord with the masterly researches of Butterworth (Proc. Phys. Soc., vol. 27, p. 410). On increasing the capacity very slowly, as resonance is approached, the deflexion falls until a value of the capacity is reached marked by a sudden drop in the current; this fall is immediately followed by a sudden rise to less than the previous value. On reversing the changes in capacity the deflexion decreases and then suddenly rises at a value of the capacity differing slightly from that at which the drop occurred as the capacity was increased. The exact point of resonance lies between these two values. This method of tuning a valve set to the resonant frequency of a neighbour- ing circuit. is a modification of Austin s well-known ˜ double click ˜ method. Both methods are described in Moullin s œ Radio Frequency Measurements, pp. 14 and 136. In an experiment on a nickel rod a metre long and 254 cm. diameter, the critical points on the condenser scale were separated by an interval of a four thousandth part of the whole capacity. On clamping the bar by means of heavy lead weights these irregularities disappear. Clamping the bar corresponds to breaking the connexions in the neighbouring circuit.Such experiments need not be confined to bars of one material; nickel or iron could be suitably attached to bars of other materials. Nor need the oscillations be wholly longitudinal; for example, a conventionally shaped tuning fork could be thrown into resonant vibration by subjecting the junction of the prongs to a vibrating magnetic field in the plane of the fork and at right angles to the prongs. The field producing magneto-striction may be due to a current carried by the magneto-strictive body. Thus when a current traverses a wire of nickel its circumference shrinks and the whole wire will therefore tend to increase in length. Thus Beatson heard a sound produced by an intermittent current flowing in an iron or steel wire (Beatson, Elect. Mag., April 1846). This reference is taken from a remark ably interesting paper by Honda and Shimizu (Phil. Mag., vol. 4, Series Six, p. 645) entitled œNote on the Vibration of Ferromagnetic Wires placed in a Varying Magnetizing Field, and published twenty-five years ago. In their paper the earlier work is reviewed and an account is also given of their own experiments on the subject carried out with such resources as were then available for experimenters. Magneto-strictive oscillations are so readily produced that it may well transpire that materials which when tested by static methods do not exhibit the effect will, when subjected to properly tuned fields, be found to possess it. For example, some variety of invar may be sufficiently magneto-strictive to oscillate in a tuned field; so that in addition to obvious important technical applications such as the provision of sources of oscillations and frequency standards, this method may be of scientific value.A paper on some parts of this very wide and fascinating subject is in

ISSN:0028-0836    

DOI:10.1038/120952a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature