摘要:

SIXTY-NINE years ago, at the British Association assembles Leech, Sir Richard Owen, the first anaomis of his age, the first anatmis/| ojjtu# a^e, pojff^^torn/on/tl theory of majzti dA^cejm; from ani a"tnropoid stock, a theory which the presidentyof, to-day, another distinguished anatomist, regards as unshakable. Since the publication of " The Descent of Man " in 1871, we have come to know more than a little of the precursors of Homo sapiens, and this direct evidence of anthropoid ancestry has been corroborated on many sides. Thus the blood of man and that of the great anthropoid apes gives almost the same reaction; in the anthropoid brain are to be recognised all those parts which have been magnified in man; we find the same vestigial structures or ' evolutionary post-marks ' in apes and in ourselves; the embryos of the two stocks develop along the same main path; the anthropoid mother fondles, mirses, and suckles her young in the human manner. " The fundamentals of Darwin's outline of man's history remain unshaken." With his characteristic frankness, Sir Arthur Keith admitted, in his carefully restrained and vividly phrased address, that we have to correct some of the early blunders. Thus man's descent has not been in a straight line; one offshoot has given rise to another after a fashion that might be compared to a cymose inflorescence. "It is among a welter of extinct fossil forms which strew the ancient world that we have to trace the zigzag line of man's descent." We no longer expect to find an orderly file of extinct stages in which every part of the body becomes, as we advance, a little less ape-like, a little more man-like. For we know that this en bloc orderly advance is not usually disclosed in evolutionary series. While one part of the body moves forward, another often lags behind.The distinctiveness of man, even of tentative men, Hominids before Homo, is in his big brain. Is there any light on the conditions of this advance? Being, as became a president, in a cautious mood, Sir Arthur Keith declared that there is not as yet any explanation to offer, yet he proclaimed with no uncertain voice that " Man has reached his present state by the action and reaction of biological forces which have been and are ever at work within his body and brain." Much depends on what is meant by " biological forces," and we wish to linger over the crucial question: How did man get his big brain? Sir Arthur referred to Sir Ray Lankester's observation that an increase in the size of the brain occurred not in the ancestors of man alone, but in diverse branches of the mammalian stock in the Miocene period. Was there at that time some environmental stimulus prompting cerebral advance, or was it the outcome of an age-long evolutionary trend in the course of which brains had largely superseded brawn? Also, is there not some elucidation in Prof. Elliot Smith's view, supported by an eloquent series of brains, from tree-shrew to ape, that the arboreal habit put a premium on variations in the direction of an increased neopallium, with special enlargement of particular areas, such as those concerned with visualising and manipulating, with a corresponding decrease of others, notably the oli'actory centre? When, also, the uplift of the Himalayas and the shrinkage of forests brought the precursors of man back to solid earth, enriched by an arboreal apprenticeship, would there not be many a reason why variations in the direction of better brains should be fostered? For these tentative men would find themselves in a new environment, with new competitors, and therefore with increased need for standing by one another in little troops. But the beginning of society served as a shield over variations which had much less chance under an each-for-himsclf regime, and over helpless stages of early infancy and old age, the former ensuring a better future through education, and the latter a conservation of traditional wisdom.Would it not be in these groups of families that the transition was made from words to language, that is to say, to the expression of simple judgments by means of socially significant imitated sounds. As these auditory symbols were added to visual ones, an incalculable addition was made to the capacity for ideation. Thinking became much easier with words as counters. So gradually the meshes of the selective sieve were altered to favour variations in cerebral capacity. That the origin of these variations remains obscure is true enough, but that is not a particular puzzle affecting the ascent of man; it applies to all emergences of the distinctively new. The frequency of cerebral variability in man is obvious in almost every family; the problem of the origin of variations is relevant throughout the whole of animate Nature. As animals become cleverer, it is increasingly possible for them to have smaller families; other things equal, an economy in reproduction has survival value. But the reduction of the number of offspring, made possible by quickened wits and enhanced parental care, favours family life and creates an atmosphere which is selective towards variations in the line of affection, kin-sympathy, and conversation. All these evolutionary processes of the subtler type work round in virtuous circles. Again, we cannot but inquire, on a more physiological level, whether there was not much shrewdness in the old suggestion of Kobert Chambers, that prolonged gestation was a factor in evolution. If the conditions of life, such as sociality or seclusion, as in elephants and Peripatus respectively, allow of prolonged gestation, there is obviously an opportunity for the offspring being born at a relatively advanced stage, able very soon to fend for itself if need be. One may contrast the newborn foal with the new-born kangaroo. This shunting back of the developing period into the antenatal arc of the life-curve allows of a safe and sequestered differentiation of the nervous system without very much being asked of it, allows of a suppression of much of the repertory of instinctive capacities, so necessary when, the creature is born at a less finished stage, and allows of the more successful development of plastic intelligence.The prolonged infancy, so characteristic of Primates, would operate like the prolonged gestation in allowing a longer period for brain development before responsibilities intrude. Even if the number of cerebral neurons does not increase after birth, there are ramifications and linkages to be established. The prolonged infancy, increasingly ensured by the incipient sociality with its division of labour, would react on the parents and help to form a sieve that favoured the wiser and kindlier variants. There is much truth in Rousseau's saying: Man did not make society; society made man. These are some of the suggestions that might be made towards an elucidation of the problem of man's big brain. If we may argue from Pithecanthropus, with his small and simple brain, the advance was not initial, but after a footing in the struggle for existence became surer. It may of course be said that variations in the regulative system-in hormone production in particular- stimulated brain development, and were associated with temporal variations in the relative length of the antenatal and infantile arcs in the trajectory of life; and Sir Arthur evidently looks to hormone-keys to open locks to which they have not yet been fitted by the evolutionist. JBut our suggestion is that more must be made of the psychical and social factors in man's emergence.What seems to us most distinctive in Sir Arthur Keith's position is his suggestion that racial evolution will become more intelligible when it is seen in the light of individual development. It is traditional to consider ontogeny in the light of phylogeny, and that illumination cannot be dispensed with; but there^has not been adequate consideration of phylogeny in the light of ontogeny. " When we have discovered the machinery of development and of growth we shall also know the machinery of evolution, for they are the same." Slight changes in developmental rate and rhythm, slight oscillations in the co-ordinating and regulating influences, slight relaxations and tightenings of hormonic control, and the developing organism is altered, as we know, both for good and ill. We understand Sir Arthur to suggest that these developmental variations have furnished the raw material which the processes of selection have sifted.There we must walk warily. Is it not the case that variations often appear in embryos before there is any differentiation of endocrinal glands, and in many organisms where hormones are experimentally unknown? Moreover, all the wobblings in developmental regulation, whether hormonic or otherwise, have themselves to be ac-tcounted for. f they are environmentally induced, will it not imply postulating the hereditary trans-mission of acquired modifications, or a remarkable persistence of the same environmental influence during the ages in which a particular trend of evolution-such as the differentiation of the neopallium-has been in progress? It may be suggested that a deeply saturating environmental influence, climatic for example, may affect the germ cells along with the body in such a way that the regulative system is perturbed. But unless we can define these environmental influences, we are almost back to Darwin's confession of ignorance, unless, indeed, we are led to an almost providential view of what has been called ' the fitness of the environment.'It cannot be doubted that a deepened knowledge of development-especially through experimental embryology-will throw light on evolution, but it "~ is going a long way to say that their problems are the same. The germ cell starts with a repertory of initiatives, including not only factors but also regulations of these, and this repertory presupposes evolution. Again, if an individual embryo suffers some regulative perturbation in a non-fatal degree, it can within limits effect automatic adjustments, but this is very different from the active way in which many an organism plays its hereditary cards in relation to alterable circumstances. There is more than machinery when a higher animal shares in its own evolution, even sometimes selecting its environment. In the evolution of the higher animals at least, the personality of the creature counts; and though the personality may doubtless be influenced by the hormones, this does not alter the fact that the organism plays its own game for better or worse. This is what Prof. James Ward was driving at in his emphasis on what he called ' subjective selection.' Sixty-nine years ago Sir Richard Owen told his Leeds audience that mankind required an altogether separate order in the animal kingdom, but what Sir Arthur Keith followed Darwin in emphasising was man's solidarity with the rest of creation. Few, we think, will read the presidential address of 1927 -dignified, responsible, and pithy-without admitting the convincingness of the evidence that "Man began his career as a humble primate animal." There is danger perhaps lest we underestimate the magnitude of this harcf-won conclusion and its mysteriousness. For we must think not only of man primitive and tentative, but also of man as minister and interpreter of Nature, man as po^t and painter, discoverer and saint. We must estimate everything by its best, and then what a piece of work is a man !Using the word emergence does not solve any problem, but it expresses a mode of becoming that has often occurred. A combination of two gases, oxygen and hydrogen, results in the production of water with entirely novel and in some measure unpredictable properties; so there has been in organic evolution a repeated origin of new types, now an insect and again a bird-resultants that seem too big for their components. Lloyd Morgan uses the word ' emergence ' to emphasise the difference between an additive resultant and an outcome that is a new synthesis. Without going back to the position of Alfred Russel Wallace, Darwin's magnanimous colleague, that man's higher qualities demand " some origin wholly distinct from that which served to account for his animal characteristics-whether bodily or mental," without seeking for this dualistically in some special ' spiritual influx,' such as operated also at the origin of living creatures and of consciousness, we may see some truth in the idea of man's ' emergence ' and apartness. He was an organic genius, a new synthesis, if ever there was one; no mechanical additive resultant, but a vital new creation, though coming but slowly to his own; not involving any breach of continuity, but making a fresh disclosure of the riches of reality-and continuing to do so. Into the fabric of humanity came many strands of many mammals, but some threads were new and the pattern was new, and it continues to evolve. But this ' emergence,' it may be said, savours of the magical,-an outcome too big for its antecedents ! Yet is tin's not one of the commonest of fallacies? We arc not slow to regard man in the light of evolution, but we have scarcely begun to envisage evolution in the light of man.To return to Sir Arthur Keith's address: it stands out as a discourse instinct with the scientific spirit; it is a fine piece of scientific tactics-to abstain, except once, from speculative discussion of factors, so that the facts might stand forth in their stability; and it is a beautiful piece of English prose, as one knew beforehand it would be, for " Le style, c'est 1'homme meme."

ISSN:0028-0836    

DOI:10.1038/120321a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WHEN Prof. Born published his " Vorles-V \ ungeii iiber Atommechanik " two years ago, atomic theory was beset with difficulties which, as one writer has remarked, were strongly suggestive of the epicycles of Ptolemaic astronomy. It was obvious that there was some inherent defect in the theory and nothing less than a radical change of outlook was required. It seemed impossible to make a quantitative determination of intensities of spectral lines on the basis of accepted mechanical pictures of atoms. Nor could the theory of dispersion be considered satisfactory, as it depended on a transcription of the various steps in the ordinary classical theory and was not built up logically on the fundamental postulates of the quantum theory. The fundamental step in resolving these, among other, difficulties was taken by Jtieisenberg soon after the appearance of Prof. Born's book. He abandoned the usual methods of calculation in terms of mechanical frequencies and such features of mental pictures as were, not amenable to observation; in fact, he virtually abandoned the usual pictures in space and time whereby an electron is here and here only at one instant, and there and there only at the next. He introduced instead a quantum mechanics involving manifolds of quantities- matrices as they were afterwards shown to be-which depended on observable transition frequencies and not on unobscrvable mechanical (or orbital) frequencies. The atom must henceforth be considered as a whole and not as a collection of individual particles each with a separate identity. The importance of th^ new step was immediately recognised and led to a rapid development of a rational, self-contained system of quantum mechanics with a remarkable simplification of the essential quantum conditions.The theory was only a few months old when a new and independent set of investigations was published by Schrodinger, who introduced another point of view. Schrodinger re-emphasised the analogy between dynamics and geometrical optics, already pointed out by Hamilton in his first researches on dynamics. But he went further than Hamilton in that he attempted to extend the analogy between mechanics arid optics to take in the concept of waves, which had proved so necessary in optics to explain interference and diffraction phenomena. Schrodinger found the appropriate generalisation of ordinary Hamiltonian dynamics, and, beginning with the simple hydrogen atom, applied it with astonishing success to a number of atomic problems. After the essentially mathematical nature of the matrix mechanics, the new treatment by Schrodinger came as a pleasant relief to many physicists, as it, at any rate, held out some prospect of the re-establishment of physical pictures of atomic processes. Although in this theory material particles are replaced by wave systems, a definite localisation of electric charge in space and time seems possible, and this with the aid of ordinary electrodynamics accounts for the frequencies, intensities, and polarisation of the light emitted by atoms without the introduction of a number of correspondence and selection principles. Furthermore, the theory accounts for the phenomena of absorption, dispersion, and scattering in a more rational way than was possible with the old quantum theory.The equivalence of the matrix and wave mechanics has now been established (principally by Schrodinger himself), and attention has latterly been directed to the physical and philosophical implications of these two aspects of atomic theory. The relation between the SchrSdinger waves and electrons seems analogous to that between radiation and light quanta. On the wave theory, one cannot answer the question as to how a particular particle moves, but one can instead find the probability of its moving in any specified direction. Whether or not this means the abandonment of the law of causality in atomic problems is a question which has received considerable attention recently, but is likely to remain for some time unanswered. In the hands of Prof. Born the new theory has yielded a satisfactory explanation of the results of Franck and Hertz on electronic collisions with atoms, and has led to a qualitative explanation of the experiments of Dymond on electron scattering. While incompetent to deal with the life history of any single electron in collision, the new theory deals successfully with a stream of electrons and may be regarded as a singular fusion of mechanics and statistics.In the light of the new work and the abandoning of cherished mechanical pictures of atomic processes, such terms as position and velocity of electrons require examining anew. Only when methods have been devised for their experimental observation will they be of physical significance. The possibility of making such determinations has recently been considered by Heisenberg, and has led him to important conclusions regarding the possibility of making simultaneous determinations of the position and velocity of a free electron. It seems that here, too, Heisenberg has opened up a new line of thought, and interesting developments may be expected in the near future. In view of these recent developments in the mechanics of the atom, it may well be asked whether any useful purpose is served by the translation of Prof. Bern's book published two years ago. The answer was given by Prof. Born in the preface to the original German text, when he said:" This work is deliberately conceived as an attempt, an experiment, the object of which is to ascertain the limits within which the present principles of atomic and quantum theory are valid and, at the same time, to explore the ways by which we may hope to proceed beyond these boundaries. In order to make this programme clear in the title, I have called the present book ' Vol. I.'; the second volume is to contain a closer approximation to the ' final ' mechanics of the atom." The material for Prof. Bern's second volume is now to hand, and students of theoretical physics will await with some impatience the completion of the task which Prof. Born has set himself. Meantime, the first volume serves as an excellent introduction to recent developments. It provides an account, at once concise and lucid, of the general dynamics of Hamilton and Jacobi, with just that special orientation towards atomic problems for which there has been a long-felt want. It introduces the reader to just those theorems of dynamics which have proved so essential in the recent developments of the new quantum mechanics.The translation has been carried out with great care under the supervision of Prof. Andrade, who has himself contributed one of the most valuable of recent introductory treatises on atomic strucwre. The book shows signs of a painstaking revision, with the result that the reader is presented with a translation which is accurate without a too slavish adherence to the original text. There are one or two minor departures from the German text, which have been necessitated by the publication of new experimental work since the appearance of the original edition. Some modifications have been made in the early paragraphs concerning the mechanism of radiation to take into account the experimental results of Geiger and Bothe, and of Compton and Simon, and there has been a modification of the derivation of theRydberg-Ritz series formula on the lines suggested by Bohr. The publishers are to be congratulated on their enterprise in producing a translation of this book, and on the efficiency with which they have carried out their task. The binding and printing are alike excellent.

ISSN:0028-0836    

DOI:10.1038/120324a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS volume completes the monumental record by the late John Venn and his son, of the sons of Cambridge up to the year 1750; it contains 42 pages of additional information in supplement to the earlier volumes. The welcome announcement is made in the preface that the Syndics of the University Press have undertaken to see Part 2 also of " Alumni Cantabrigienses "-for the years since 1750-through the, press. There are not so many famous names in science in the present volume as in the earlier ones: we note John Wallys, one of the founders of the Royal Society; Samuel Wegg, its treasurer for thirty-four years; Edward Wright, of Mercator's projection; Francis Willoughby, the distinguished naturalist, fellow traveller with John Ray: William Turner, the scientific pioneer in botany; Robert Smith, founder of the Smith's prizes; Nicholas Sanderson, who lost his eyesight in infancy from smallpox, yet became later Lucasian professor; and William Whistori, Newton's successor in the same chair, who was banished from the University for his Ariaii views. We note that T. Tudway, organist of King's and professor of music, was deprived of his chair for making puns on the queen, but he afterwards recanted and was readmitted.Robert Taylor, who perfected the cure of ague by quinine and was physician to Charles II., is one of many distinguished medical men who figure in the volume, and it is noteworthy how frequently the letters F.R.C.P., F.R.S. are coupled together. Another prominent group are the divines, among whom may be mentioned William Tyndal, the translator of the Bible; Archbishop Whitgift; Samuel Wesley, father of John and Charles; and Thomas Sheppard of Emmanuel, in honour of whom Cambridge, Massachusets, was so called. The names of Edmund Spenser, John Suckling, and Edmund Waller remind the reader of the place of Cambridge as a nursery of English poetry, while Laurence Sterne and W. Stukeley recall other literary activities. Echoes of bygone times are found, in the record of Job Tookey, admitted at the age of thirteen years in 1658, removed after a fortnight, apprenticed to a grocer in Cheapside".a,nd later sent to sea, or of Henry Sumpter, sent froni King's- College to JSlew College, Oxford, where he was thrown into a cave under the College where salt fish was kept-and died not' long afterwards. A more modern touch is sadly supplied by F. Sterling, Fellow of Jesus, killed in the War in Flanders in 1692. The names of Sir Robert and Horace Walpole; of Thomas Went worth, Earl of Stafford; and of George Villiers, Duke of Buckingham, recall the historical background; while Richard Whittington, Lord Mayor of London, figures in the volume as one of the early benefactors to the University. Cambridge owes a deep debt of gratitude to the authors of these volumes for their zeal, learning, and accuracy, and the services of the University Press.ui/Bpublishing them must not be forgotten.

ISSN:0028-0836    

DOI:10.1038/120325a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE seven-days week is a division of time which has long been in general use, and is commonly believed to have come down to us frorv at least the time of Moses, but why or how the days have become associated with the planets- ,be word planet is here used as understood by the ancients-is not so generally known. Mr. Colson's book supplies an immense deal of information on this point, and is obviously the result of a great deal of study and research. The author's purpose is to show that our present week is a combination, which took place within the Roman Empire, of two distinct systems-the Jewish week and the 'planetary' week. The former had long been familiar to the Romans, but the latter, as he shows, cannot be traced back much earlier than the beginning of the Christian era, and was due to the development among the masses of astrological ideas as to the influences of the planets.The accepted order of the planets according to their distances from the earth, starting with the outermost, was Saturn, Jupiter, Mars, Sun, Venus, Mercury, and Moon, but this order is not at first sight evident in the sequence of the names. There are successive jumps over two planets, but a suggestion of Dion Cassius is accepted as probably correct, namely, that the planets were supposed to rule successively for one hour at a time. Thus starting with the first hour of Saturn's day (Saturday) Saturn itself was regent, but Jupiter presided over the second hour, Mars over the third, and so forth, which brings the first hour of the second day under the regency of the sun (Sunday). Similarly, the opening hour of the third day will be ruled by the moon (Monday), and the order of the names throughout the week is thus readily explained. It is suggested that originally the point of contact between the Jewish and the planetary weeks was the Sabbath. It is shown that by the beginning of our era the idea had become widespread that that day was Saturn's day, and this may perhaps have given the planetary week its starting point. Among other matters of interest in the book we find the discussion of such subjects as the week in the New Testament and the early Church, and the establishment of Sunday as the Lord's Day. With reference to the latter, while acknowledging that by the second century the first day of the week had acquired an undoubted sanctity as that on which the Resurrection took place, the author concludes that we owe our religious and civil Sunday to the combination of two factors, namely, " the immemorial familiarity of the Jewish Christian with the Sabbatical week, and the recent familiarity of the Gentile Christian with the planetary week." There is also an instructive chapter on the week in northern Europe, and the names of the days in various European languages are collected together into five groups in the appendix.The book is extremely well written and contains much information not readily accessible to the ordinary reader. Its' usefulness would have been still further enhanced by the addition of an index or a synopsis of the chapters.

ISSN:0028-0836    

DOI:10.1038/120326a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS book is very well written, in simple vivid language, and the author is at his best in the descriptions of particular customs, ceremonies, and beliefs. The chapters on sexual life, betrothal, and marriage; the accounts of fishing and gardening, of feasts and dancing, of warfare and magic, are one and all excellent. The description of bonito fishing, so characteristic of the Southern Solomons, is of outstanding literary merit, and scientific interest. The abstract subjects, such as kinship and legal or economic organisation, suffer from a weak grasp of sociological principles. The table of kinship nomenclature is well-nigh worthless,- in that it gives the native words for English appellations instead of giving a sociological analysis of the native terms. The author is right in correcting the late Dr. Rivers (on p. 59) on the use of personal names between relatives in some parts of Melanesia, a custom which is by no means confined to Dr. Ivens's area. But when he adds that " relationship terms in these places (Sa'a and Ulawa) do not connote social duties," he contradicts his own evidence, and his mistake is due to an obvious misunderstanding of Dr. Rivers's words and ideas. Equally misleading are certain generalisations about native ' shell money.'On the whole, however, the book is a valuable contribution to Melanesian anthropology; it provides very attractive reading, and is magnificently filled with illustrations in colour and black and white, with diagrams and maps.

ISSN:0028-0836    

DOI:10.1038/120327b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE aerofCut's need of a knowledge of weather is vital, tjnt the ordinary meteorologist when trying to provide for it finds it difficult to put on one side the conventional modes of treatment and to remember what is really wanted: thus when describing the upper winds at any place, he is tempted to give the mean wind direction at successive heights, instead of a table of the relative frequencies so that the pilot may know the likelihood of a favourable wind. However, Mr. Gregg has admirably realised the situation. After ail account of the general circulation and of the methods of observation, he naturally deals with American conditions, discussing the vertical structure of the air (but the constancy of e/P on p. 31 should be explained), the change of winds with height and gustiness, fogs and clouds (the photographs of these being excellent), visibility, thunderstorms, cyclones and anticyclones, forecasting, and flying over the North Atlantic and the north polar regions. His ' moving thunderstorm ' corresponds with what is called in England a ' line squall,1 but its width is given as. 40 to 50 miles, the length being 150 to 200 miles. The chapter on cyclones is essentially practical, though interesting theoretical questions are raised by the predominance of rain to the JST.W. of the centre, instead of to the S.W. and S.E., which the Bjerknes theory suggests. We wish that such a book were available for those under British conditions.

ISSN:0028-0836    

DOI:10.1038/120328b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

ON Sept. 8, 1926, between 21h30mand 22h, Greenwich mean time, I saw from Bygdö, near Oslo, a remarkable aurora in the west. It had the form of a portion of a feeble arc of grey violet colour, stretching upwards from the horizon about 40°. Later on this arc changed into a diffuse mass sharply limited on its south border.Simultaneously, this aurora was very carefully observed from the Lerwick observatory as faint streamers on the northern, eastern, and western part of the sky up to zenith. I was fortunate enough to have two of my aurora stations in action, Bygdo and Oscarsborg, mutual distance about 26 kilometres, and I obtained of this remarkable aurora a series of photograms of the greatest interest. The measurement and calculation of the photographic plates will appear shortly in Ger-lands Beitrdge zur Geophysik, and I will here only mention the principal results.The arc appeared on the plates as a curtain of rays which were difficult to distinguish visually, and this curtain was situated over and to the north-west of the Shetland Islands at the quite unusual height of 300 to 500 kilometres. The diffuse form which ended the aurora display probably reached the immense height of more than 1000 kilometres. This high curtain was essentially different from all curtains measured in southern Norway from 1911-1922; in fact, these curtains generally had a yellow-green colour and were situated from 80 to 200 kilometres above the earth. The situation of the curtain far in the west, some hours after sunset, led me to the supposition that it was perhaps illuminated by the rays of the sun. My assistant, Ragnvald Wesoe, made at my request the necessary calculations, and the hypothesis was verified: the aurora was situated in that portion of the upper atmosphere directly illuminated by the sun.It was now an interesting question to know if the aurora rays, measured during the years 1911 to 1922 and of unusual altitude from 400 to 800 kilometres, were also exposed to the rays of the sun. Mr. Wesoe calculated the height of the dark portion of the atmosphere for each ray whose situation had been calculated from photograms J and the results are as follows: The rays situated in the interval from 400 to 800 above the earth were all exposed to the sun's rays, and of those stretching from 100 to 400 kilometres, about 95 per cent were in darkness. This remarkable fact is most clearly seen in Fig. 1, which gives the situation of all the aurora rays from 20h 21m, Greenwich mean time, on Mar. 22, to 2h 53m on the following day. Each ray is marked by a vertical line, and an arrow indicates that the lowest or highest point of the rays were outside the photographic field. The boundary between the dark and sunlit atmosphere is marked by a short stroke the height of which is the mean between the heights corresponding to the highest and lowest measured point of the ray. In this first approximation no account has been taken of refraction.From this diagram it is clearly seen that the height of the rays is great in the evening and in the morning, but low during the night. The high rays in the morning of Mar. 23 were of a beautiful blue colour, and through a small pocket spectroscope I saw a quantity of lines in the blue and violet, while the common green aurora line was rather faint. I am sorry that I had used all the plates on the other stations, so that only a very few photograms of these blue rays were taken. But judging from single photographs, the rays later reached heights probably exceeding 800 kilometres. FIG. l.It seems from these facts that the sunlight has a remarkable action on the upper atmosphere, so that the illumination caused by the electric rays forming the aurora borealis became visible to much greater altitudes than ordinarily. It is well known from wireless telegraphy that sunlight ionises very strongly the higher atmosphere, and it may be that the accumulated ionising effect of the sunlight and of the electric rays illuminates the atmosphere to a greater altitude than tho electric rays alone. Perhaps also the ioiiisatiori lifts up the atmosphere by electric charge, as in Vegard's theory, or pcrlmps such a- lifting up may be the effect of a raising of the temperature in those regions. A detailed study of photographs of the spectra of these high rays may solve the question as to the cause of this effect of sunlight on the altitude of the aurora.See “Résultats des mesures photogrammétriques des aurores bortéales observées dans la Norvège méridionale de 1911 à 1922”, Fig. 12, Geofysiske publikationer, vol. 4, No. 7

ISSN:0028-0836    

DOI:10.1038/120329a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE surprising fact that fragments of volcanic rock occur in the barrier reef of Tahiti, as reported by Dr. Crossland in NATURE for April 23, must be welcomed by all students of that remarkable structure; but that fact does not, it seems to me, prove the “original continuity of the present barrier reef from the [island] shore to the ocean slope” outside the reef, as is stated in his second letter in the issue of July 2. The fact only permits the inference that the lagoon was formerly filled in some manner, perhaps by stream deltas instead of by a broadened fringing reef, so that island detritus could be transported to where the barrier now stands. This inference involves so extraordinary a series of changes from former lagoon filling to later lagoon excavation—for which there is no other satisfying evidence provided—that even the inference should not be accepted as valid until all other possible means of explaining the occurrence of the volcanic fragments have been excluded. Further details as to tho nature of the fragments and the manner of their occurrence are desirable.Dr. Crossland's rejection of the physiographic evidence for the subsidence of Tahiti, as provided by drownod-valley bays and as given in my account of the island (Annales de Geographie, 27, 241-284; 1918), seems to me of a piece with the neglect of such evidence on the part of Murray, Chippy, A. Agassiz, and other students of coral reefs; and that neglect was clearly the result of their unfamiliarity with physiographic evidence rather than of its weakness. Regarding the occurrence of embayed valleys, my observations in 1914 led me to be just as positive in asserting their presence near the isthmus which connects the two cones of the Tahiti doublet as Dr. Crossland is in asserting that " There are no bays in Tahiti." The bays to which I refer are " little bays which," as Dr. Crossland says, " open out of Port Phceton,'.' and inasmuch as they enter well back of the general shore line of the island between eroded slopes of volcanic rock, I took them to be the partly drowned valleys of ordinary streams, and so still regard them, in spite of their being described as " peculiar " by Dr. Crossland and as " certainly not drowned valleys." But I fully agree that Port Phjeton Bay: is merely a re-entrant space between the two confluent volcanoes of which Tahiti is composed. This origin was by no means overlooked in my article, for I there said that Port Phaeton Bay on the south-west side of the inter-cone isthmus and the corresponding Taravao Bay on the north-east side of it "sont evidemment en rapport avec la forme initiale des deux cones contigus " (p. 245). When the small bays which open out of Port Phaeton were produced by the entrance of sea water into their little valleys in consequence of a moderate subsidence of the island, all the many larger valleys of the island were presumably embayed also; but they have all been rilled with alluvium, because the drainage areas tributary to them are larger and more mountainous. The small bays, which still remain but partly filled, appear to have escaped complete filling because they receive streams from small drainage areas. Of course the many bay-filling deltas have a seaward slope. Indeed, the associated facts that the delta flats are in no case level and that their streams have a rapid flow along them, both of which Dr. Crossland mentions as if to discredit the origin of the flats as the fillings of farmer bays, have no such bearing.On the other hand, a number of the delta flats are a quarter or half mile wide at their mouths; and that so great a width should there be given them by the lateral erosion of their streams, while the streams still flow in sharp-cut v-valleys upstream from the flats, seems to me unreasonable. The more reasonable explanation of the flats is, as above stated, that they are the fillings of valleys that were embayed by island subsidence; and this explanation is all the more reasonable in view of the absence of a shallow rock platform in front of the great cliffs in which the inter-valley spurs have been cut back by former wave action around most of the island circumference. I am glad that Dr. Crossland has recognised these " old marine cliffs," for they have generally been overlooked by earlier observers, excepting Agassiz; indeed, at least two observers have explicitly stated that there are no sea cliffs at the base of the island slopes. Surely, a rock platform must have slanted gently seaward just below sea-level when the cliffs were cut back by the ocean waves during a reefless period in the earlier history of the island; the absence of reefs at that time being presumably due to the abundant outwash of detritus from the non-submerged valley mouths, as is to-day the case in the reefless island of Reunion. But instead of being now fronted by such a platform, the cliffs of Tahiti are fronted by a lagoon twenty or more fathoms in depth, even though the lagoon-floor has been aggraded by an unknown measure of detrital deposits derived from the island and the reef. Evidently, therefore, the cliff-base platform has subsided to a greater depth than that at which it was originally cut, and this subsidence must have been the same as that which produced the now delta-filled valley embay-ments. The cliffs as at present seen must plunge below sea-level.As to my interpretation of the slopes of white sand inside of the Tahiti barrier reef as evidence of inwash from the reef, and as therefore contradicting the idea that the lagoon is now suffering excavation, I am by no means persuaded that it is erroneous. Agassiz' account of his dredgings in the lagoon lead to the same conclusion, for its floor contains much detritus from the island. If other parts of the inner slope of the barrier reef than those which I saw are devoid of inwashed sand, that may perhaps be because the. reef is there broader, or because the sand has been shifted by lagoon waves down the slope from the reef to the middle depths of the lagoon floor. But regarding this point, as well as the blocks of coral rock on the sand slopes, I will wait for the appearance of Dr. Crossland's fuller report, which I will examine with the same interest that I hope he will give tcrmy book on " The Coral Reef Problem," shortly to be published by the American Geographical Society of New York. He will there find many details concerning my observations on- numerous Pacific reefs, the present lack of which he is good enough to regret. In the meantime I may refer him to a rather lengthy article on the coast and reefs of New Caledonia in the Annales de Oeographie for 1925; and also to a small book on the Lesser Antilles, with particular regard to their imperfect barrier reefs, published by the American Geographical Society in 1925. But the details that I give are chiefly physiographical rather than biological. That side of the problem I am not prepared to deal with; and in any case it seems to me the less significant side, so far as reef origins are concerned; for it is to the forms and the changes of the island coasts, as determined by abrasion, erosion, and movements of upheaval or subsidence, that the reef-builders must adapt themselves. Dr. Crossland is fully warranted in saying, so far as my published articles show, that I seem " to have missed the cliffs " on the north side of Moorea, a smaller island than Tahiti, not far north-west from it; for in my Tahiti article it is unfortunately asserted that " aucune falaise n'entaille les contreforts " of the smaller island (p. 277). Nevertheless I saw and sketched the north-coast cliffs of Moorea, as will appear in my forthcoming book, and I have even ventured to explain their local occurrence as the consequence of a prolonged attack by the sea on the north coast after the subsidence of the island had begun, because the two largest valleys of Moorea open on that side, and the abundant detritus that they have discharged must have drifted westward from the valley mouths and formed a beach along the shore, thus preventing reef growth and permitting continued cliff cutting there, although, in consequence of subsidence, reefs already been formed by upgrowth around the rest of the shore line and protected it from abrasion. It is because of this subsidence that the lower cliffs, which were presumably cut all around the island in its unprotected youth, are no longer visible. Cliffs are seen to-day only on the north side where, as above suggested, the continuation of abrasion after subsidence had begun gave the cliffs a greater height than elsewhere. This explanation is rather venturesome, but it is better than none. In view of my failure to mention the north-coast cliffs of Moorea, Dr. Crossland concludes that my " criticism of Daly's theory of glacial control . . . fails in this case." By no means; but I must leave that long story for more deliberate presentation else where. Suffice it to say now that the absence of cliffs from most of Moorea and from many other reef- encircled islands in the true coral seas of the Pacific not only contradicts the glacial-control theory, but also goes far toward proving that the partly sub merged cliffs of Tahiti were not cut back by low-level abrasion in the glacial period. It is only in the marginal belts of the coral seas that cliffs due to low- level abrasion are to be found, as I have shown in the above-cited booklet on the Lesser Antilles and else where.1 In conclusion, let me add that I accept Dr. Crossland's dictum that "barrier reefs can no longer be taken as an index of subsidence without independent proof from the adjacent land; " and it is precisely because such independent proof is almost universally forthcoming that the upgrowth of barrier reefs as a consequence of island subsidence may be generally accepted, essentially as Darwin long 'ago inferred.

ISSN:0028-0836    

DOI:10.1038/120330b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WE have found that a fine tungsten filament at a very dull-red temperature placed in a stream of nitrogen undergoes a considerable (10.25 per cent.) lowering of its resistance (for constant current flowing through it) when active nitrogen produced up-stream by a condensed discharge passes over it. At the game time the colour changes to a much duller red, that is, the radiation is decreased. These changes persist until the filament is momentarily flashed at a white heat, whereupon the original condition is regained. Apparently a surface layer of some sort forms on the filament and produces a lowering of its temperature. The resistance of the filament at room temperature is the same either witli or without the layer.The same cooling effect can bo produced by bombarding still nitrogen with electrons from another source filament accelerated by suitable electric fields. In a tube with largo nickel electrodes which had been thoroughly degassed by the repeated use of an induction fxirnace, this effect was first detectable when the exciting electrons had an energy of 11 volts. The rate of formation of the layer increased rapidly with the voltage. In a second tube, in which the anode was a hot tungsten spiral, the effect was not detectable below 22 volts. The effect was independent of the potential of the testing filament, showing it to be produced by a neutral substance. It seems possible that in the first case the active substance was produced at the low voltage by bombardment of the metal surfaces. These effects were obtained both with commercial nitrogen which had been passed over hot copper and with nitrogen prepared by Waran's method which was so pure that it woxild not give the afterglow, Peculiar current-voltage characteristics were obtained with the tube having the hot anode. With increasing voltage the current increased, as in other gases, up to 22 volts, at which voltage it began to fall off. At 25 volts an arc struck, the current took a sudden rise immediately, followed by a decrease in two or three seconds to a value considerably below that which it had had before the arc struck. Further increases in voltage produced slight increases in current. Upon decreasing the voltage, the current dropped oft' until the arc broke at about 20 volts. Here there was a sudden decrease in current followed by a slower rise to a much higher current, the same as that at the corresponding voltage before the arc had struck. The two currents were the same for lower voltages. That those effects are characteristic of nitrogen and not ascribable to charges on the walls of the tube seems probable, for no such effects were observed with argon in the tube. A decrease of the thermionic current in nitrogen at much lower pressures and higher voltages was observed by Laiigmuir (Phya. Rev, 2, p. 450; 1913). Wo also observed a considerable temporary decrease in the thermionic emission from a tungsten filament as ordinary activo nitrogen passed over it.A tube was constructed having a pile of tungsten foil discs, spaced apart, and mounted so that they could be flashed with the induction furnace. Electrodes and filaments were provided, so that the nitrogen could be activated either by the disruptive discharge or by electron bombardment of known voltage. Gas pressures were measured with a hot wire guage of small volume. The total volume of the tube and gauge was small enough in relation to the area of tungsten that a gas layer one atom deep on the latter, if evaporated, would cause a pressure of the order of p-1 mm. The tube was baked out under exhaust, as usual, at 450° C. and the discs well degassed by flashing. With a few tenths of a millimetre of nitrogen in the tube, and keeping the discs at a dull-red heat while the spark discharge was passed, a partial clean-up of the gas was obtained. After exhausting the remaining gas and closing off the pump, the discs were flashed, with the discovery of a considerable quantity of gas. Gas so recovered was not cleaned up by a hot tungsten filament, and on examination with a hand spectroscope gave all evidences of being nitrogen. The experiment was repeated a large number of times, varying the time of the spark discharge. Tn all cases except where the time of discharge had been very short, the amount of gas recovered on flashing was a: constant quantity, approximately that to be expected from a layer one atom deep. Exactly the same results were obtained by activating the nitrogen with an are at 25 volts. At 15 volts there was no indication of clean up, or of a gas layer on the tungsten which could be removed by flashing. Our conclusions are that a clean tungsten surface at a dull-red heat, if placed in an atmosphere of nitrogen, activated either by a condensed discharge or by an electron bombardment at more than 22 volts, becomes covered with a nitrogen layer of the order of one atom deep. The effect of this layer, at this comparatively low temperature, is to cool the surface. It seems probable that it does this by allowing the surface to conduct more heat to the gas, i.e. by increasing the accommodation coefficient. At relatively high temperatures, the same layer is probably so unstable that only a small fraction of the surface can be covered at any one time, but it acts to increase the work function. The flashing of a filament covered with Such a layer in the neighbourhood of a clean filament causes the production of a layer upon the latter. Apparently the layer evaporated by flashing comes off in an active form. These experiments suggest that active nitrogen can bo produced by bombardment of nitrogen gas with 22 volt electrons, but further work is necessary to establish this conclusion. The experiments are being extended and completed, and will be described in detail later

ISSN:0028-0836    

DOI:10.1038/120332a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

As absorption measurements proved to be the key to a complete analysis of the arc spectra of neon and argon, we recently extended the use of the method to include an investigation of the spectra of krypton and xenon.As in the case of neon and argon, we found that some lines in the spectrum of krypton were powerfully absorbed by this same gas when a weak electrical discharge was passed through it. With xenon similarly stimulated, selective absorption of spectral lines was also observed. Even a casual glance at photographic spectrum plates obtained with both gases showed this weakening of selected lines. As was to be expected, lines in the visible spectral region were scarcely, if at all, absorbed.. Examples of spectral lines, showing strong absorption by the method indicated, are, in the case of krypton, XX7601, 7854, 8104, 8112, and in the case of xenon, XX8231, 8819. The degree of absorption that took place in the case of other spectral lines is being determined from microphotometric observations.In our analysis of the spectrum of xenon, the wave-number difference 9140 was observed between pairs of wave-lengths with the following frequencies: r 11167, (11977, r 12675, (13655, / 13664, / 15371, \20307, \21117, \21815, \22795, \22804, \2451U(16177, / 16181, /17552. \25317, \25321, \26692.The wave-number difference 9140 is the same as that between the wave numbers of the resonance lines XA1469-9 and 1295-8 found by Hertz. The pairs of lines are therefore Sapt and S4pi (i=l to 10) lines expressed in the old notation originally used with neon. The infra-red wave-lengths Sspt and Sspt involve a metastable state, but wave-lengths showing strong absorption are found among them. The results given above go to show that the structure of the spectra of the heavier rare gases krypton and xenon corresponds to that of the spectra of the lighter ones neon and argon, namely, a '£" normal state a 3P012 state comprising 2 metastable sub-levels, a 'P, state, etc. There is, of course, a much larger separation between the 3P012 and 'Pj levels with krypton and with xenon than with either argon or neon

ISSN:0028-0836    

DOI:10.1038/120333b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature