摘要:

THE mild controversis Which have been excited by Sri Ardhur Keiths modarate and cautious preside­a ss to,British Association at Leeds Suggest that Science and scientific method are still regarded wi me suspicion by the educated portion of the community. We need not take seriously the objections to the theory of evolution raised on sentimental or religious grounds in so far as these arise from prejudice and belief in authority. Science can recognise no authority, and can admit no barrier to the free and fearless use of the intelligence. The theory of evolution stands or falls on the stubborn and irreducible facts and upon the rational interpretation of them, and we need have flO fear of the verdict of any impartial and competent jury, as Sir Arthur Keith has well and truly pointed out. Another note has, however, been sounded by the wiser critics a note not so much of antagonism as of doubt whether scientific method has, after all, proved an adequate key to the problems of the universe and of practical life. The Bishop of Ripon has voiced with great frankness this doubt of the adequacy of science. In hinting that the world could get on perfectly well if for ten years every physical and chemical laboratory were closed, he had in mind apparently two things first, that the progress of science has vastly increased the complexity of mans material environment without improving his moral outlook or adding to his happiness, and second, that not only educated laymen but also specialists themselves are so overwhelmed with the rush of new discoveries, new conceptions, that they have no time to envisage the results as a whole, to co-ordinate them and see them in their proper relation to other human activities. He suggested in reference to the first point that the patient and resourceful energy displayed in the laboratories could be turned to better effect if it were applied to the human and social problems of the day, where clear and resolute thinking is so much required. With this contention we do not propose to deal. Ne sutor supra crepidam is a sound, if unheroic, maxim.It is rather with the second point that we wish to come to grips, and particularly with the suggestion emphasised also by several writers in the Times that science is suffering from neglect of philosophy, to its own detriment and to the lessening of its influence on human thought and character. Dr. Burroughs, in the sermon referred to, asked whether amid all our new discoveries we do not sometimes seem to have lost our sense of direction: How many of our sectional explorers ever ask themselves which way lies the whole l Am I wrong in thinking that the several sciences increasingly feel the need of a philosophy to co-ordinate them? Twenty or thirty years ago, this suggestion that science might learn from philosophy would have been received with scorn in scientific circles. There was a spirit of confidence abroad, a conviction that the principles which had served so well and had led to such conquest over Nature were established beyond question; philosophy was branded as metaphysical and dealing in vain abstractions. We find an echo of this great period in Dr. Chalmers Mitchells provocative and vigorous Huxley Lecture, where he roundly asserts that philosophy, since she was judicially separated from science, although retaining the title lover of wisdom, has made no positive addition to knowledge and has only been a spinner of vain words and barren ideas. This intransigent attitude is, we venture to think, rather unusual at the present day. The last twenty years have seen the foundations of physics torn up and rebuilt, and the change has come about not only by the press of new knowledge, but also to a great degree through keen hard thinking about the fundamental conceptions of the science, through true philosophical criticism, carried out by the physicists and mathematicians themselves. We can no longer rest content with the simple materialistic schema which satisfied Descartes and Laplace. As Prof. A. N. Whitehead writes in his remarkable book, Science and the Modern World:The progress of science has now reached a turning point. The stable foundations of physics have broken up. . . . The old foundations of scientific thought are becoming unintelligible. Time, space, matter, material, ether, electricity, mechanism, organism, configuration, structure, pattern, function, all require reinterpretation. What is the sense of talking about a mechanical explanation when you do not know what you mean by mechanics? Yet Dr. Mitchell would have us cling tenaciously to the mechanistic method in biology, on the ground that only through its aid has come any positive increase of knowledge. This is not the occasion to discuss in detail the merits and the shortcomings of the mechanistic method in biology; we may, however, remark a propos of Dr. Mitchells lecture, that his polemic against vitalism mostly misses the mark, for the alternative to biological materialism is not necessarily a dualistic vitalism, but some form of organismal or emergent theory, all of which he confounds under the common ban.The mechanistic method, however, is itself an interpretation of Nature. It is, to use Dr. Mitchells own words about vitalism, a proclamation of a belief and not an inference from observation. Its sole justification is the practical one, that it does up to a point help us to understand the activities of living things. But there are other methods of explanation possible, and it is unwise to rule them out as unscientific. Since physics has found a revolution in its fundamental concepts necessary, it seems dangerous for biology to cling to the cast-off beliefs of the nineteenth century physicists. It must come to terms, too, with psychology, and give up the, hopeless attempt to derive conscious behaviour from tropisms and conditioned reflexes, regarded as purely physical happenings. The time is indeed ripe for a critical revision of biological concepts. We need not fear that this will lead us into mystical by-ways. It is probable that there will always be something left unexplained even Dr. Mitchell doubts the possibility of the part interpreting the whole but clear thinking not only about the facts of observation, but also, more important still, about our own methods of interpretation, will help to reduce and render manageable the mysteries of organic life and evolution.Shall we call this criticism of conceptions science or philosophy? This brings us to the heart of the matter, and to our tentative conclusion, which is that the nineteenth century divorce of science from philosophy is good for neither side, and that co-operation should now be the order of the day. The benefit will be mutual. There has been some justification for the jibe that philosophy deals with words and abstractions, and is apt to be negle tful of the laboriously garnered harvest of scientific fact. In the recent discoveries both in physical and in biological science, there is ample material to keep the philosopher busy for years. The man of science for his part can learn much from the philosopher. He can learn how biassed and provisional his views of Nature may be, how difficult it is to get rid of irrational presuppositions which may colour all his thought. In his eloquent tribute to Huxley, Dr. Mitchell points out that He accepted, as a postulate, but admitting it to be a postulate, belief in the rationality of the universe our minds seek to explore. This was the charter of science, conferring a certain right in return for the observance of certain duties. The right was that the writ of science should run whatsoever traditions, beliefs, dogmas, or customs it might destroy. The duties were accurate observation, clear statement, a logical scrutiny of generalisations so that they should not imply and should not seem to, imply an iota of necessity; an open mind for new facts, but a cross-examination of the evidence for them the more ruthless in proportion to their apparent contradiction of widely based generalisations: and above all a profession of ignorance in preference to the propounding of acceptance of causal principles which could not put to the test of experiment. That is well said, but it does not go far enough. Let the clear thinking and the logical scrutiny be applied not merely to the generalisations resulting from observation and experiment but also to the underlying conceptions, the basal philosophies, in accordance with which these generalisations are formed. Let us scrutinise everything even our most cherished scientific principles.Coming back now to the broader question of the relation of science to other forms of human activity, we must recognise the limitations of scientific and indeed of any purely intellectual method. There are other aspects of human personality which science does not satisfy, and it would be foolish to extend the dominion of scientific method beyond its proper sphere. We do well to remember that the richness of reality is inexhaustible, both in its manifestation in the external world and in the depths and recesses of personality. Neither science nor philosophy can give more than an abstract and colourless rendering of essential truth, which is approached perhaps most nearly by creative art. But inside these necessary limitations the exercise of the intellect should be free, fearless, and untrammelled by any dogmatism, prejudice, or dependence on unrealised assumptions. 1 "Logic and Law in 3iology. Huxley Memorial Lecture, 1027. Pp. 30. (London: Macmillan and Co., Ltd., 1927.) 18. net.

ISSN:0028-0836    

DOI:10.1038/120573a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

AS a result of the great change which has taken place in recent times in the nature of the beer favoured by the public, the demands on the skill of the modern brewer are much more exacting than they were on that of his predecessor of a generation ago. The brilliant and well-conditioned beer of to-day is characterised from the brewers point of view by a low original-gravity, low alcohol-content, and low hop-rate. These factors, combined with the lack of nutrient matter in the modern wort, place a greater strain on the yeast, and also render the beer more liable to infection. On the other hand, modern scientific methods have provided a weapon with which to combat these difficulties. These are the influences traceable throughout the volume under review, and mark a stage in the passage of brewing from an art to a science. The book appeared in its original form so far back as 1877, and was intended at that time essentially for the novice. In 1892 it was revised and enlarged under the title A Handy Book for Brewers, but the author, H. E. Wright, died at the time of the publication of the third edition in 1907. In the twenty years that have since elapsed the information has naturally become out-of-date, and the appearance of a revised and augmented work is to be welcomed. The plan and scope of the last edition has been followed fairly closely, though the student rather than the brewer is catered for.The first chapter sketches in outline the complete brewing process, and should prove useful to the beginner if studied in conjunction with the synoptic table at the end of the book, since the brewing operations are dealt with in order in more detail in the subsequent chapters. Brewing-room calculations, chemistry, hydrogen ion concentration and ferments in general provide additional chapters, and the book closes with a brief, elementary description of the brewery and its plant. In a book which attempts to cover so vast a subject and its ramifications, in which the details of the methods used are largely matters of personal opinion based on experience, a is not difficult to pick out omissions and errors. On controversial points, however, the author has apparently endeavoured to strike a balance between opponents and to produce an argument that is not too bewildering for the beginner. This has involved the omission of a great deal of the most recent investigations on subjects such as starch, yeast, and the preservative powers of hops, though a readable account is given of the earlier work. Again, for example, reference might with advantage have been made to the vexed question of the Marout barley, which in spite of its favourable analysis, appearance, and powers of resistance to extremes of climate, has been condemned in many quarters. The disposal of brewery by-products is also of sufficient economic importance to justify its inclusion.The author is at his best when he deals with the varying conditions which influence the practical side of brewing. His descriptions of chemical operations, however, are often lacking or out-of- date. We doubt whether the student will be able to obtain the required degree of accuracy from many of the instructions with which he is provided, especially if his intelligence is assumed to be of such a level that he has to be told which end of the thermometer to insert in the drying-oven! A redeeming feature of the descriptions of the applications of science to brewing is the chapter on hydrogen ion concentration, the theory of which is outlined clearly by F, A. Mason. Its usefulness, however, will be largely obviated by the fact that the practical applications of the theory occupy only half a page of this chapter, and nowhere else in the book are they mentioned. This is a serious drawback when subjects such as mash-tun treatment, stability of beer, and the optimum conditions for enzymes are under discussion. It is unfortunate that the book is characterised throughout by an extremely loose form of grammatical expression which at times renders the meaning almost unintelligible. Minor errors and misprints are far too numerous also, and the spelling of many words is rendered correctly in some parts and differently or incorrectly in others. Proper names (Buchner, Marsh-Berzelius, etc.), and the title of Pasteurs classical work on beer, are among the more serious offences in this last respect. There is a lack of references to the original literature, and the frequent mention of a glossary which had to be omitted at the last moment is confusing. There is also a paucity of illustrations, the few given being chiefly photographs of plant. The briefest description of the anatomy of the barley-corn, or of the hop, is incomplete without a diagram.The book is well produced, but the advertisements, which have invaded even the end-papers and the backs of the titl contents pages, are an eyesor.

ISSN:0028-0836    

DOI:10.1038/120575a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS important book is the result of considerable experience in the teaching of plant pathology, which is now a recognised feature of agricultural and horticultural training. The ar- rangement and treatment of the subject matter follows that adopted by Dugger in his well-known C Fungous Diseases of Plants, and has been used by the author in hi classes during the last ten years. The book is divided into four sections, the first containing two chapters dealing respectively with the history of pathology and the symptoms of disease; the latter especially should be read by all students of the subject. Section 2 deals with non-parasitic diseases, caused by some unfavourable influence in the plants environment. The effects of excess and deficiency of available nitrogen and potash in the soil are discussed at length, and examples are drawn from sand drown of tobacco, yellow berry of wheat, and potash hunger of potatoes and tobacco. It is perhaps unfortunate that the important problem of leaf scorch of orchard trees finds no place in the discussion, A considerable amount of useful information is given in other chapters setting out the effects of Un- favourable air, light, temperature, and water conditions upon plant growth. Bitter pit and scald of apples are excellent examples of the treatment given to individual disorders. The phenomenon of photoperiodism, which has attracted much recent attention, is briefly described in three pages. One may perhaps doubt the advisability of including it in such a book, where space is valuable, but if it is worth discussing at all in relation to plant disease, these pages seem quite inadequate for the purpose.In dealing with diseases proper, the author has selected those which are of economic importance, and has described the history, distribution, symptoms, etiology, host relations, and control of each, together with a list of references at the end of each disease and a brief note of etiologically related diseases at the end of each chapter. The lists of references to literature are extensive, but they are mainly concerned with American investigations, Reference to foreign papers seems desirable, Section 3 is devoted to virus and related diseases. Only those who have struggled with the mass of literature on this subject can appreciate Dr. Healds difficulty in compiling a reasoned account of these fascinating diseases. He has succeeded in giving the elementary studert an insight into the subject, which should stimulate his interest and appreciation of its importance, Section 4 occupies two-thirds of the book, and is devoted to parasitic diseases, including those caused by bacterial pathogens, which are classified in accordance with Migulas scheme. Actinomyces scabies is, however, included among the bacteria. Fungus diseases are treated admirably, with good arrangement and up-to-date material. Students should have little difficulty in obtaining a good working knowledge of plant diseases. The section ends with a discussion of diseases caused by parasitic seed plants and nematodes, but the latter chapter does bare credit to the importance of these animal pests. Investigators have the greatest difficulty in distinguishing between parasitic and non-parasitic forms present in diseased material, and many harmless forms have been convicted of evil intent without proper trial. Students should be warned against this.A good general index is provided, but there is no host index. The volume is well illustrated, and the illustrations are usually effective, but Figs. 199-202 are decidedly poor and are not calculated to inspire the student. The object of teaching plant pathology is to train workers to diagnose and control diseases which are causing serious damage to economic plants the world over. This being so, an effective text-book must include a clear account of the physiology of disease and the principles of disease control. It is regrettable that Dr. Heald has purposely omitted this part of the teaching of pathology from his text-book, which will doubtless be used by many teachers of the subject.

ISSN:0028-0836    

DOI:10.1038/120576a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

MANY circumstances invest the present volume LtL with signal importance. Of such an unusual magnitude has been deemed the investigation which it reports, that a special grant was assigned to it by the Carnegie Corporation; and for the last four years Thorndike has so devoted himself to it, as even to give up for its sake his university teaching. Moreover, as indicated above, his entire staff has been collaborating with him. The account of all this work begins by freely conceding that hitherto mental tests of the intellect have been afflicted with three fundamental defects: ignorance of what is being tested; ignorance of how the test-scores should be combined; and ignorance of what the results signify in respect of the intellect.To cope with this situation, the authors in the first place conceive the iiitelleci as having two dimensions: on one hand altitude; on the other, width. By the former they mean the degree of difficulty at which a person can succeed at tasks; by the latter, the number of taska that he can succeed with at any specified degree of difficulty. So far, all is plain sailing enough. But now have to be encountered the fundamental defects. For these concepts of altitude and width of intellect can serve no useful purpose until we settle what kinds of mental performance the word intellect is really intended to comprise. On this vital point the authors commence in a surprising fashion.For a first approximation, let intellect be defined as that quality of mind (or brain, behavior, if one prefers) in respect to which Aristotle, Plato, Thucydides, and the like, differed most from Athenian idiots of their day. How the mental make-up of these idiots shall ever be ascertained is left unsaid.Later on, however, a more definite view is advanced and made the actual basis of the present investigation. It is to the effect that every one can take intellect to mean whatever he will. What abilities and tasks shall be treated as intellectual is essentially a matter of arbitrary assumption or choice at the outset. . . . After the first choice is made, tasks not included in it, and not even known, may be found to correlate perfectly with the adopted total, and so to be intellectual.The authors themselves select as their first choice what they call intellect CAVD, composed as follows. C. To supply words so as to make a statement true and sensible.A. To solve arithmetical problems. V. To understand single words.D. To understand connected discourse, as in oral directions or paragraph reading. To the study of this intellect CAVD, then, the whole investigation is really directed, and a very remarkable result is the outcome. Evidence is adduced that these four abilities, C, A, V, and D, jointly constitute one single total-ability, in the sense of a unified, coherent, fundamental fact in the world.With great interest the reader turns to examine upon what sort of evidence such a result has been founded. It consists in the discovery that the different altitudes of the intellect CAVD correlate with one another to a degree which on due correction for attenuation by random disturbances is little if at all short of perfect unity. This line of evidence in respect of the originally adopted intellect CAVD is just the same, it will be noticed, as that which our previous quotation gives for making any subsequent additions to the purview. Now comes a curious point which the authors appear to have overlooked. It is that this kind of evidence perfect correlations after being corrected for attenuation is precisely that which was introduced by the present reviewer in first demonstrating the existence of what our school calls g. Even the various criteria used afterwards for this purpose (including the latest, that of tetrad differences) are merely diversified mathematical forms of expressing exactly the same thing. (For proof of this statement, reference may be made to the reviewers recent work, The Abilities of Man.)It only remains, then, for Thorndike to carry out his programme and ascertain what further abilities correlate perfectly with his initial CAVJJ, when the correction for attenuation is effected in a suitable manner. Assuredly he will find, just as we have done in the book just referred to, that the range includes all abilities whatever. Tn this way his unified, coherent, fundamental fact in the world turns out to be our g once again, nothing more or less. Hereby is completed the entire chain by which, link after link, the school of Thorndike has been gradually adopting all the chief doctrines long advocated by ourselves. In such an eventful convergence of originally warring views, we may venture to see a most hopeful augury for the future of psychology as a positive science.

ISSN:0028-0836    

DOI:10.1038/120577a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE eighth volume of this monumental editiqn has the melancholy distinction of being the last that was published in the editors lifetime. It shows no diminution of the accuracy which always distinguished Dr. Dreyers work. The editor calls it the third volume of the Epistolae Astronomicae, a series which is here continued from June 1597 to June 1601 , four months before Tychos death. The plan of this volume is the same as that of the second volume of the Epistolae, the seventh of the whole series, but the subject matter is largely different. While the second volume was mainly occupied by letters written while Tycho was steadily pursuing his observations at Hveen, supported by liberal emoluments and aided by numerous assistants and workmen, in this volume he is a traveller, seeking a new home in which to continue his work. We find him first at Rostock, then at Wandsbeck, afterwards at Benatky, and finally at Prague; and it is natural that his correspondence should be largely concerned with negotiations for reconciliation with his former patron the Danish king, or with the view of securing a new patron, such as he eventually found in the Emperor Rudolf II. We have also the correspondence relating to the equipment of the observatory at Benatky.For the life of Tycho, these letters are most interesting. They have the further interest that they introduce us to Kepler, whose first letter to Tycho, accompanying a copy of his Mysterium Cosmographicum, begins on p 14 of the volume, and whose last letter in October 1600 ends on p. 385. As the connexion thus established with Kepler was the most important, it might be said the only valuable result of Tychos removal from Denmark, and as it resulted in the discovery of the laws of planetary motion, it is very gratifying to find this correspondence set in its place among Tychos astronomical letters. The most interesting letters in this correspondence are perhaps Tychos critique of the Mysterium Cosmographicum and the testimonial which Tycho gave Kepler in June 1600. Both have been published among the collected works of Kepler and are well known to students of the history of astronomy. Tn the former letter (pp. 44-46), Tycho, in the most courteous way, cast doubt on Keplers theory of the connexion between the planetary spheres and the five regular solids, because it rested on Copernicuss values for the distances and eccentricities, which were seriously in error. He also objected to any doctrine of orbium realitas, that is, to any reality of the spheres, and regarded the immense distance to which the Copernican hypothesis relegated the socalled eighth sphere, the sphere of the fixed stars, as an absurdity which by itself would destroy the whole theory. He suggested that Kepler should continue his line of study, including the eighth sphere in his harmony, and invited his eooperation. In the same letter Tycho declared that the reason for his removal from Denmark was to prevent the destruction of his astronpmical treasury collected through so many years with such great labour and expense. With our great store of observations it is difficult to realise the uniqueness of Tychos work, so far exceeding anything that had survived from the ancient or that seemed likely to be attempted again in the modern world.The editor, in addition to his usual brief but pertinent comments, has in this volume given us an alphabetical biographical index of the principal people named in the astronomical l«tters. The twelfth and thirteenth volumes complete the collection of Tychos observations. A flysheet issued with the last of these and dated 1926, Sept. 25, records how Dr. Dreyer before his death on Sept. 14 had requested the presidents of the Society of Danish Language and Letters to present this last volume of Tycho Brahes treasury of observations to the Carlsberg Institute on Sept. 25, the fiftieth anniversary of its foundation, in gratitude for the munificence with which it had provided for the publication of the greater part of the works of the famous Danish astronomer.The two volumes of observations contain not only Tychos observations, but also several by Fabricius, and a few collected by Kepler. There are also two catalogues of stars, but Tychos complete catalogue appears elsewhere. Probably the most important part for present-day astronomy is to be found in the 107 pages devoted to observations of seven comets. These observations at least can never be superseded by observations of other comets made with better instruments

ISSN:0028-0836    

DOI:10.1038/120578a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

DURING the last few years the art of telephony has made gigantic strides and the future of the telephone industry seems very promising. iIany engineers first acquired their working knowledge of the subject from the earlier editions of this well- known handbook. It has gradually ircreased in size, although much obsolete and obsolescent matter has been cut out in each edition. In this latest edition the book has been increased by 146 pages and more than 100 illustrations. Although the book is becoming more technical and more mathematical, it can still be recommended for the beginner. The rapid progress of automatic telephony in Great Britain has taken even experts by surprise. A few years ago it used to be urged that its secrecy, which is really one of its greatest advantages, laid it open to the practical joker who could play silly tricks with impunity. In the United States the trouble had proved to be a real one, and special laws were proposed to frighten the jokers. An unscrupulous business man also might cause the line of a rival to test engaged ant times of the day. Luckily these defects have been completely remedied. To scientific men the use that telephonists make of phantom circuits to increase the number of conversations that can take place simultaneously between two stations always seems wonderful. The authoritative account of trans-Atlantic telephony given in this book will prove helpfulto many. The saving of costs of trunk lines by means of thermionic valve repeaters is shown by the fact that in place of aerial lines weighing from 100 lb. to 800 lb. per mile, there are now underground cables working between London and Glasgow and between London and Berlin weighing only about 20 lb. per mile.

ISSN:0028-0836    

DOI:10.1038/120579b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

Dr. SHANHAN has succeeded in producing a book on uth America that was much needed. After some preliminary chapters on the continent as a whole, including a most interesting one on historical geography, he treats South America by natural regions, thus avoiding much repetition which a treatment by States would entail. The book bears evidence of wide and discriminating reading, but it gives the impression of a corn- pilation and lacks signs of personal acquaintance with South America. Many of the broader human interests receive little notice, such as the immigration problems, the racial problems, and the character and peculiarities of the great cities and seaports. Cities are not merely market places; they have individualistics that are worthy of portrayal even in a geographical work, if geography is to escape the charge of being merely the background of commerce. But in spite of these criticisms we welcome the book, especially for its freedom from bias towards any particular interest or State, a defect which mars too many works on South America.

ISSN:0028-0836    

DOI:10.1038/120580c0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS communication concerns the magneto-optical effect, described by me inScience(N.S. vol. 53, No. 1382, pp. 565 to 569, June 24, 1921) and NATURE, June 23, 1921, p. 520, which was at that time a novel discovery or observation. The description was later followed by a statement of “Further Investigations” (Science, N.S. vol. 54, No. 1387 , pp. 84–85, July 29, 1921).In the first place I desire to make a correction in the latter communications, where it is stated that the flickering observed appears to keep time with the cycles and not with the alternations of current. This is an error, as it was found later that the described fluctuations do follow the alternations, the mistake being due to misinformation as to the cyclic rate. It may be desirable here to describe briefly the original phenomena, adding comments which relate to more recently observed facts. A magnetic field produced by a direct current, permanent magnet, or by interruptions or alternations of current, is rendered visible even when very weak, by a light smoke from an iron arc; such fume or smoke being effective for the purpose even when so thin or diffused as to be scarcely noticeable in the air. Such smoke, diffused in the space where a field exists, when illuminated from above by sunlight or an artificial source and viewed iii a direction across the light beam and more or less normal to the direction of the lines of force of the field, appar ently becomes luminous, but in reality becomes a far better reflector diffuser in certain directions of the incident light than when the field lines are absent. Viewed along the magnetic lines, no increased luminosity is produced even when the field is strong or the illumination strong, or both. The condition for its observations seem to be:(1) Illumination transverse (more or less) to the direction of the lines of the field. (2) Viewing in a direction more or less transverse to the lines of the field and to the direction of the incident light.The amount of iron smoke in the air required to produce a very noticeable effect seems to be very small, although density of the smoke increases greatly the contrast between what is visible when current or field is on, and when no field exists. Indeed, without the presence of the field the smoke from the iron arc may be practically invisible. The illumination from the smoke particles was found to be polarised as if produced by reflection from strings of fine particles, oriented in the direction of the field lines. These particles are exceedingly small, almost beyond ordinary high powers of the microscope, and the striated ferric oxide, which it seems to be, can be caught on a microscope slide while the magnetic field is on, and studied under high powers. The remarkable thing is the small amount of the iron smoke needed to produce the effect and the instantaneous response to very weak fields. Thus, if an open coil or helix without a core of iron be traversed by a fluctuating or slowly alternating current, the flickering may be shown by a detector constituted by holding the open neck of a glass flask over an iron arc for a few moments. Some of the smoke enters the flask, which can then be corked. Such a flask has shown flickering at a distance of twelve feet away from the small coil, through which a low frequency current was sent; and, curiously, when the flask was placed near the coil, the flickering was replaced by a steady illumination. When gradually removed from the coil in the direction of its axis, the flickrring became more and more pronounced.This indicates that the orientation, or arrangement of the particles to correspond with the field lines, takes place with a weak field, and almost instantaneously in a strong alternating field, in the latter case being accomplished and maintained throughout the whole wave of current. The zeros seem to be without effect in arresting the appearance, while at a considerable distance away from the same coil, excited as before, the weaker field at such a distance can only orient the particles at or near the maxima of the current waves. This seems to indicate that a certain very low value of the magnetising force is sufficient for the orientation or alignment of the particles. Retention of vision by the eye may also cover up any very short interruptions in the luminous effect itself. Use has been made since the publication of the original descriptions of the effect for rendering visible to the eye a rotating field produced by biphase, three- phase, or polyphase currents. The effect is unique, and it can be photographed.In the accompanying illustrations, Fig. 1, a, shows a box with a glass front and back, a beam of light being sent in from the back with no excitation or magnetic field present; Fig. 1, b, shows the same with the coil lying flat on the top conveying current. In this case it is clear that a luminous effect, displaying the field of the coil, has been depicted. In each case, of course, iron arc smoke has been within the box at each trial; it being allowed to enter through a hole at the bottom of the box seen indistinctly in the figures. It is surprising, too, how long a time it takes for the fumes to settle out of the air within the apparatus. FIG. 2.In Fig. 2 is shown a device for rendering visible a rotating field, such as that of a three-phase motor. The structure at F is, in fact, a field winding, clearly showing in the photograph the three entering wires for its excitation. As the ordinary frequencies would be too high for observation, the rest of the figure to the left shows a small motor M drivingat reduced speed a small generator 0 of the three-phase currents needed for the excitation of the field at F. Usual arrange- ments are provided for varying the speeds, and thus the cyclic rate or frequency of the currents in F The interior of F is arranged with glass ends so that it may receive illumination from the back, and also that it may receive and retain iron arc smoke. In this way the revolving field inside the structure F becomes distinctly visible by a luminous glow revolving within it. The direction of revolution may also be instantly changed by the switches provided for reversing two of the phases, and the speed of revolution of the field may be made slow, or so fast that retention of vision results in a continued interior luminosity.It is probable that with further development, such arrangements may be designed to make use of this magneto-optical phenomenon in the study of distortIons in alternating fields by the introduction of closed circuits in the form of rings, plates, and various forms of conductors, or even to compare the distortions produced by the material as well as the form of con- ductors in alternating fields. Perhaps, also, the distortions of field lines produced by revolving or moving conductors in even direct current fields may be exhibited or investigated. My time has not permitted much work, interesting as it may be, to be carri

ISSN:0028-0836    

DOI:10.1038/120581a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN his letter to NATURE of Oct. 1, p. 473. Mr. I. S. Bowen has made the important suggestion that several of the chief lines in the spectra of gaseous nebulæ may be due to what spectroscopists have called ‘forbidden’ combinations of terms in the spectra of ionised nitrogen (N II), ionised oxygen (O II), and doubly-ionised oxygen (O III). It is, of course, no longer permissible to suppose the existence of hypothetical elements to account for the long-standing mysteries of nebular spectra, and we must accordingly regard the nebular lines as being produced by known elements under conditions of excitation which have not yet been imitated in the laboratory. It has seemed natural enough to look to the lighter elements, and those who, like myself, have given special attention to the spectra of these elements under widely varied conditions, have doubtless kept in view the possibility of finding some indications of nebular lines in the course of their observations. Extensive experiments, however, have failed to reveal any traces of them.The evidence put forward by Mr. Bowen in favour of ionised oxygen and nitrogen is already very substantial and demands careful consideration. The case for 0 III is, in fact, a good deal stronger than appears from his letter. I have lately been investigating the structure of this spectrum, and it may be of interest to refer to some of the results obtained. Doubly-ionised oxygen has six external electrons, and some of the more important configurations (in n orbits), with the corresponding types of terms predicted by Hunds theory, are shown in the following table, the notation being that adopted in a recent paper on N TI (Proc. Roy. Soc., A, vol. 114, p. 662).1. 2, 2,. 31 3, 3,. Terms. 2 2 2 sp 1F, iD, 118,2 2 1 1 p s 1P,1, lP1 2 2 1 1 sp.p iD,1 2P, 1S, 2D, lP, 2S,2 2 1 1 p . d 11F43, iD, lP21, 11E3 11D, PF1 Without reference to the nebular lines, I have deter mined all of the terms on the second, third, and fourth rows, besides others, from my own (unpublished) observations. lJtilising Bowens observations in the extreme ultra-violet, the values of the three deepest terms follow as a matter of course, but are less accurate in consequence of the difficulties of measure- ment in this part of the spectrum. For the 1P terms Bowen has found j82 1F1 193, j31 PP, 116, and the two green nebular lines are attributed by him to 0 III because of their separation zXv 193. Hts thus identifies the nebular lines with the forbidden combinations 1J*2 _ iD2 and 1P1 I iD2, but, the value of iD2 being thOn undetermined, he gives no additional evidence in support of this view.From singlet combinations in the extreme ultra- violet previously suggested by Bowen (Phy. Rev., vol. 29, p. 241), in combination with the values of JFl and 1P since determined by myself, it is readily found that 11D, 424385, and 1S = 401472. For the nebular lines, on Bowens view, we thus have XLA,500684 199671 1P2 iD2 495S91 201601 iP1 11D,.Hence, 1P, 444352, j31444545, 1P0 44466i. The assumption as to the nebular origins in question can be tested by the lines X3057 and X3743 previously suggested by Bowen as probably representing the regular combinations PP 13D and 1P 1P respect- ively, using the values for 1L and 1P which I have determined. Unfortunately, each of these combinations yields six components, which cover but 029 A in the first multiplet and 036 A in the second. and so have not been resolved. However, the calculated wave-numbers for 13P 13D range from 326986 to 327295, and compare very favourably with the observed line X3057, for which 3271 18. Similarly, the lines 13F PP range from 267134 to 267584, and are in good agreement with 267165 representing the observed line X3743. These considerations appear to give strong support to the view that the two green lines of the nebuke are due to 0 III, but no further tests appear to be available at present.The agreement in position of the nebular line X436321 with the combination iS 11D2 of 0 III is as close as can be expected, and further tests would seem to depend upon the possibility of measurements of lines in the extreme ultra-violet and in nebuhe with a still higher order of accuracy. The evidence for attributing the nebular lines X65836, X6584 1 to N TI appears to be very convincing, but the published observations of the N II spectrum in the extreme ultra-violet are inadequate to provide further tests.Bowens assignment of the strong nebular lines X372891, X372616 to 0 II leads to term values for I 2D, of the expected order of magnitude, and the consequent calculation of the red line X7325 may be provisionally considered to support the suggested identifiations. Owing to the apparent absence of regular intercombinations of doublet and quartet terms, however, the only test at present available would seem to be the discovery of one or more companions to the nebular line X7325. If the identifications be correct, there should be a satellite about 10 A distant on the less refrangible side of this line, and a second chief line in a position which cannot be predicted because the separation of the 22 terms has not yet been determined. The numerical evidence, on the whole, thus appears to be in favour of Mr. Bowens suggestions, and it is interesting to note that if these should be fully confirmed, the observations of nebula may be used to determine the structure and exact positions of certain unresolved lines in the extreme ultra-vi

ISSN:0028-0836    

DOI:10.1038/120582a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN searching for evidence that would enable a decision to be made as to the exact distribution of the electrons responsible for the series of fifteen ‘rare earth’ elements from lanthanum to lutecium, the colour of their salts appears to be of prime importance, particularly as it is known that colour is intimately associated with movements of electrons in atoms. The fact that many of the rare earths yield coloured salts has led to considerable uncertainty as to their proper place in the periodic classification, and many attempts have been made to allocate them to appropriate periodic groups on the grounds of valency, isomorphism, and colour analogies.I have recently shown (Jour. Chem. Soc., Sept. 1927) that the foregoing fifteen rare earth elements are all analogues of scandium, the last fourteen of them forming an anomalous subseries of the transition subperiod of the third long period of the classification. This arrangement rules out any possibility of allocating these elements to more than one periodic group. It follows, in consequence, that the rare earths have no real relation to any other series of elements and that the observed colour resemblances are fortuitous.Examination of the colours of the salts of these elements from this new viewpoint has brought to light colour squences hitherto unrecognised, the sequence of colours of the salts of the first eight rare earths being identical with that of the last eight in reverse order. Lanthanum, cerium, praseodymium, neodymium, illinium, samarium, europium, and gadolinium salts are colourless, colourless, green, red, unknown, yellow, faint rose, and colourless respect- ively, while those of lutecium, ytterbium, thulium, erbium, holmium, dysprosium, terbium, and gadolinium show the same colour sequence, with the apparent exceptions of terbium and holmium. The salts of terbium, the 7th member of the 2nd series, are recorded as colourless, but in thick layers they are almost certainly faintly rose, for they exhibit absorption at the blue end of the spectrum. Terbium is thus analogous to europium, the 7th member of the 1st series, the salts of which are either faintly rose or colourless and exhibit absorption mainly at the blue end of the spectrum.The salts of holmium, the 5th member of the 2nd series, are known to be yellow, whereas the salts of the recently discovered element illinium, the 5th member of the 1st series, are as yet unknown. From the duplicate colour sequence, however, it may be predicted with confidence that illinium salts when obtained will be yellow like those of holmium. The yellow colour predicted for illinium salts may partly explain why illinium was not sooner detected in the intensive researches on rare earth separations of thelast century, for samarium, with which it is naturally associated, is nearest in atomic weight, yields yellow salts, and probably exhibits absorption in the same spectral region. As the duplicate colour sequence shown in the following table relates to the trivalent ions of the elements, the numbers in the 1st column are the actual numbers of electrons inthe atomic numbers). 54 La, 68 Lu colourless 0, 14Ce, O7Yb , 1, 13 56 Pr, 66 Tm green 2, 1257 Nd, 65 Er red 3, 11 58 Ii, 64 Ho yellow 4, 1059Sa, 63Dy , 5, 9 60 Eu, 62 Tb faint rose 6, 861 Gd colourless 7 0+1, -1 +2, 2+3, -3 +4, 4+5, -5 +6, 6J=7 (0, 0), (6, 8)(1, 0), (6, 7) (2, 0), (6, 6)(3, 0), (6, 5) (4, 0), (6, 4)(5, 0), (6, 3) (6, 0), (6, 2) (6, 1)In the 3rd column are shown the numbers of electrons in the ions after deducting the 54 of the La ion (xenon structure.). The 4th column shows the variation of these electrons from 0 and I 4, cerium for example having 1 electron and ytterbium 1 (1 less than 14). The identity in the colour sequences indicates that the same colour is obtained in two different ions when one has as many electrons more than zero as the other has less than 14. There being only two colour sequences, it may be regarded as certain that the 1 4 electrons concerned are arranged in only two sets or subgroups. Further, as gadolinium is the only element common to both sequences, being the last of the first sequence and the first of the reversed sequence, it may be inferred not only that gadolinium has electrons in both subgroups, but also that the second subgroup begins when the first is complete. As gadolinium has 7 electrons and lutecium 14, it follows that the former has the sub- group structure 6, 1, and the latter 6, 8. The complete distribution of the 14 electrons in the rare earth elements is given in the last column of the table.It can be no more than a curious coincidence that the number of electrons in each ion from gadolinium to lutecium is expressed by the same figures as the numbers of electrons in the two subgroups, the gadolinium ion, for example, having 6 1 electrons and the subgroup structure 6, 1. In Bohrs theory of atomic structure, the maximum number of subgroups in a quantum level is equal to the quantum number, and the maximum number of electrons in a subgroup is equal to twice the quantum number. In the 4-quanta level there should thus be 4 subgroups of 8 electrons each, this structure being attained in lutecium by the increase of 3 subgroups of 6 each to 4 of 8 each, thus involving four types of subgroup change though only two types of change are evident from the duplicate colour sequence.Early in 1924 I pointed out that the experimental fa ts of emission and absorption X-ray spectra indicated a number of quantum subgroups invariably greater than is given by Bohrs rule. The intensities of the emission lines and the widths of the absorption bands further indicated that the numbers of electrons in subgroups could not be equal, evident also from the fact that the number of subgroups in a level is always an odd number, while the total number of electrons in a level is always an even number. I deduced that the 4-quanta level must contain 7 subgroups of 2, 2, 4, 4, 6, 6, 8 electrons, and suggested a new law of uniform atomic plan that the maximum number of subgroups in a quantum level is equal to one less than twice the quantum number, and that the maximum numbers of electrons in subgroups is equal to twice the natural numbers taken in duplicate, the last and largest subgroup being unduplicated and equal to twice the quantum number. This law was supported by relevant chemical evidence, and has since been confirmed by Stoners work on spectral multiplicity. The foregoing electronic structures for the rare earth elements, as deduced from the duplicate colour sequence, fully confirm the law of uniform atomic plan, the subgroups for the 4-quanta level being 7 in number and. consisting of 2, 2, 4, 4, 6, 6, 8 electrons as in lutecium. The arrangement of the ra:re earths into the foregoing two series accords completely with their analytical separation into two groups, the cerium earths lighter and the yttrium earths heavier than gadolinium. Detaih of the division of the rare earths into the two series on other chemical and crystallo graphic grounds will shortly be submitted to the Chemical Society.1 Hopkins, in Chemistry of the Rarer Elements, p. 107, gives the colour of dysprosium salts as bright green. This is an error, all being in fact golden ye

ISSN:0028-0836    

DOI:10.1038/120583a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature