摘要:

THE recently published correspondence between the Bishop of Birmingham and the Arch- bishop of Canterbury has not been without interest for students of sheds some light upoi altitude clthe authorities of the English Church towards the results of scientific research. We are ofcourse not concerned in these columns with spiritual faith or denominational belief, but itis appropriate to make clear the attitude now presented by leaders in the Church towards progressive scientific knowledge, and the best method of doing this may be to quote certain relevant passages from the correspondence in question. In parenthesis, and as a sign of the new spirit which now prevails between leading representatives of science and theology, it is- sufficient to mention that Sir Arthur Keith, president of the British Association, is totake the chair on Monday next at a lecture to be delivered by Dean Inge on the subject of "Scientific Ethics." Dr. Barnes's first letter to the Archbishop, occasioned by the outburst at St. Paul's Cathedral on Oct. 16, contains the folio-wing observations:"One cause of the weakness of the Church has arisen from the apparent determination of teachers to ignore scientific discovery. Though all competent biologists accept man's evolution from an ape-like stock, the theological consequences of such belief are still seldom stated. I set myself years ago to expound these consequences and to show why they did not seem to me to upset the main Christian position." To this the Archbishop replied that the Bishop was disturbing himself unnecessarily, since evolu - tionary views had won wide acceptance amongst religious people, and were now no novelty."I believe that you overrate the adherence of thoughtful people to creation theories of fifty to a hundred years ago, and I scarcely think that among those who listen to you there are a great number who hold the opinions which you satirise. For myself, at least, I can say that your position on the biological question, in outline and so far as I understand it, is one with which I personally have been familiar for more than fifty years. Believe me, this teaching, however admirable, is to most of us not novel." Although these remarks may be said to have evaded the issue raised by Dr. Barnes, yet they constitute a valuable pronouncement, admitting as they do the theological legitimacy of evolutionary opinions; and they were immediately welcomed as such by Dr. Barnes in his reply."I would publicly thank your Grace for your letter in answer to my own. By tacit acknowledgment of the truth of the biological doctrine of evolu't%ri your Grace removes from Christian ministers of oi Church any qualms in proclaiming it." Dr. Barnes then returnedto the point alluded to in his former letter, a point whii the Archbishop had allowed to escape him."Of course in my sermons I have sought to emphasise not so much the doctrine itself as the readjustments of Christian dogma consequent upon its acceptance." Since no official reply has been published to this further letter of the Bishop of Birmingham, the Council of the Churchmen's Union, a body of theological liberals under the presidentship of the Very Rev. Dr. Inge, Dean of St. Paul's, dispatched a letter to Dr. Barnes, which contained the following remarks:"You are blamed for preaching evolution to general congregations. Now it is true that the accepted teaching of science on this subject has long been familiar to educated people who find no difficulty in reconciling it with the Christian faith. But the acceptance of evolution as a biological theory is often unaccompanied by any attempt to follow up the consequences of the theory in their bearing on traditional theological statements, and we believe that in making the attempt you are doing good service which is greatly needed at the present time."The correspondence from which the foregoing extracts have been given seems to indicate a somewhat anomalous state of affairs. While biological theories of the evolutionary origin of man, and indeed of creation generally, appear to prevail among educated members of the Church of England, clerical as well as lay, no systematic attempt is being visibly made to modify the traditional dogmatic system in view of the new knowledge which radically affects it. The pressing miture of the need for such theological restatement in view of knowledge which, as the Archbishop reminds us; is fifty years old, can escape no reflective person. We have onlyto consider how integral to the traditional dogmatic system is the doctrine of a historical fall of man. The Christian theory of human nature (that is, its need of supernatural grace, and so on) hangs upon it; while the scheme of redemption, involving a historical incarnation, is its dogmatic correlative. It is not merely a question of the earth having been created in six days or during incalculable periods of time that issue, though it has beenconsidered serious, is trifling compared with the others raised by the theory of evolution.There has, of course, been much literature published dealing with different aspects of the subject. Dr. N. P. Williams, the Regius professor of divinity at Oxford, devoted his recent " Bampton Lectures" to a historical and philosophical treatment of the doctrine of original sin: a book characterised, as Prof. W. R. Matthews has observed, by "its frank acceptance of modern views of the world and its repudiation of ideas which have long been accepted in the Church." Canon Streeter also, in his book "Reality" (192E), includes some remarkably stimulating chapters which deal quite frankly with the problems of man's relation to Nature, and, above all, of the problem of evil of which the Genesis myth is an attempted solution. This problem, which is so radically affected by evolutionary theories, Canon Streeter rightly regards as more important than any other for religion. Thus evolution touches the very heart of religion, and cannot be disregarded by religious teachers who take their task seriously. If we may be permitted another example, it may be found in Dr. Major's "English Modernism," a work which contains lectures recently delivered at Harvard. Dealing with new ideas of creation, he registers " the acceptance of evolution as the Divine creative method, and the abandonment of instantaneous creation by successive Divine fiats"; and he observes that this "entails the acceptance of the fact that the creative process is still proceeding." This view, "although it seems modern, appears to underlie the theology of the Fourth Gospel," and is also in harmony with the remarkable passage in the eighth chapter of Romans, where creation is spoken of as still travailingin birth-pangs.Yet in spite of these and other sincere and able efforts to find a new expression of Christian truth in terms of evolutionary science and philosophy, it seems to be widely held in authoritative circles (1) that the new doctrinal view should be disseminated only with extreme caution and reserve, and (2) that restatements of dogma would at present be highly dangerous. It would seem to be against this overcautious policy that Dr. Barnes is in revolt. Tn advocating the bolder course, he will certainly have the sympathy of men of science, who are quite accustomed to frank restatements of doctrine; indeed, science has progressed by means of them. As for the fears expressed for the faith of the weaker brethren, a remark made many years ago by Prof. Harald Hoffding seems apposite: "No one wants to rob the poor man of his ewe lamb only let him, remember that he must not drive it along the high road unnecessarily and then demand that the traffic should be stopped on its account."

ISSN:0028-0836    

DOI:10.1038/120717a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WE welcome the appearance of a work on the history of medicine by Dr. C. 0. Cumston, who, in addition to other qualifications for the task, was president of the fifth International Congress of the History of Medicine held at Geneva in July 1925 (see NATURE, Nov. 14, 1925, p. 729). The book is divided into twenty-one chapters, in which the writer successively discusses Egyptian medicine, Hindu medicine, Greek and Roman medicine, Islamic medicine, medicine including physiology, anatomy, pathology, nosology, therapeutics, and surgery in the sixteenth and seventeenth centuries, and the principal medical doetrines of the seventeenth and eighteenth centuries. A special chapter is devoted to the doctrine of irritability, the Brunonian theory, and naturalism, and another to organicism and vitalism. The concluding chapter consists of a brief survey of the evolution of therapeutics.After an introductory chapter on the evolution of medicine, showing how it gradually advanced through the theological and metaphysical stages before reaching the positive stage described by Comte, Dr. Cumston devotes a chapter to Egyptian medicine, in which he shows how the history of the healing art is to be found in the various papyri. The following chapter on Hindu medicine contains numerous quotations from the Vedas relating to medicine, such as the account of tie birth of the Hindu IFsculapius, the duties of he physician and nurse, plastic operations, and the legend of Jivaka, which shows that the operations of major surgery were at least known if not actually carried out by the ancient Hindus. The next chapters deal with Greek medicine, commencing with the philosophers, such as Theophrastus, Pythagoras, Heraclitus, Parmenides, Alcmeon, Empedocles, and Diogenes of Apollonia. A special chapter is devoted to the Hippocratic oath, which has always been the guide of the medical profession. In the following chapter, which is concerned with Hippocrates and the Hippocratic Collection, Dr. Cumston points out that naturalism was created from the time that Hippocrates demonstrated the existence of a formative, conservative, and medicative power inherent in the organism, by which it feels, reacts, and develops, preserves itself, and combats morbid causes and the effects produced by them. Among the direct successors of Hippocrates, with whom the next chapter deals, may be mentioned Aristotle and his disciple Theophrastus, who con- tributed indirectly to the progress of medicine by their studies in natural history, Diodes of Carystus, who was one of the first to make a scientific study of anatomy, and Praxagoras of Cos, who was one of the last of the Asclepiada whose name has been preserved. More importance, however, attaches to the school of Alexandria, of which Erasistratus and Herophilus were the most illustrious representatives, as it was from this school that the systematic study of anatomy emanated.An interesting survey is given in the succeeding chapters of medicine in ancient Rome, including the practice of Asclepiades, whose system was based on the teaching of Eicurus, the school of methodism founded by Themison and also represented by Thessalus, Athenaus of Cilicia, Archigenes of Apameia, Soranus, the author of a work on diseases of women, and Ca1ius Aurelianus, who wrote on acute and chronic diseases. The chapter on Galen contains an instructive comparison between him and Hippocrates. According to Dr. Cumston, Galen would certainly have equalled the father of medicine if he had had less imagination and independence of character, and had not been influenced by the philosophy of Aristotle. Galen explained facts by hypotheses, whereas Hippocrates observed the phenomena of Nature without explaining them. The result has been that the doctrine of Hippocrates has survived, but Galen's system of medicine has been completely destroyed. In the chapter on Islamic medicine, Dr. Cumston controverts the view that the Arabians were merely servile copyists of the Greeks, and maintains that in addition to their methodical classification of the scattered elements of Greek medicine they created clinical medicine and enriched pathology with a knowledge of new diseases.The medical schools of Salerno and Montpellier next receive attention, an interesting description being given of Trotula, Constantine the African, the Regimen Sanitatis, Roger of Parma, Guy de Chauliac, Sylvius, and Rabelais. The chapters on medicine in the sixteenth century contain an account of the work of Jean Fernel, the author of "Universa Medicina"; Fracastor, the first scientific writer on the doctrine of contagion and author of the celebrated poem on syphilis; Paracelsus, who helped in the advancement of medicine by introducing mineral substances into therapeutics; and the great Italian anatomists. In discussing the medical doctrines of the seventeenth century, Dr. Cumston maintains that the three great contemporary schools of medicine, namely, the iatro-chemical, iatromechanical and vitalistic, and animistic schools, owed their existence to the three great philosophers Van Helmont, Descartes, and Leibnitz.Dr. Cumston distinguishes three periods in the eighteenth century to illustrate the progress made in anatomy and physiology. The first period was that of direct continuation of the researches carried Out during the seventeenth century, and was represented by Littr , Duverney, Verheyen, and especially Winslow and Snac, who discovered the muscular fibres and valves of the heart. The second period was represented by Albreeht von Hailer, who published his work on sensibility and irritability in 1752; while the third period, which covered the last twenty-five years of the eighteenth century, was remarkable for the discoveries of Lavoisier, Fontana, Priestley, Fischer, Vauquelin, and Abernethy. Dr. Cumston may be congratulated on having succeeded in presenting the general reader and student of medicine, for whom the work is intended, with an admirably clear and thoughtful introduction to the study of medical history. The text is accompanied by excellent portraits and other illustrations, most of which are from the author's private collection.

ISSN:0028-0836    

DOI:10.1038/120719a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE curious and beautiful insect fauna of Australia is perhaps the most attractive in the world. That of New Zealand, notwithstanding certain features of special interest, is on the whole rather disappointing and very defective, but its treatment in conjunction with the Australian relieves this difficulty. Both faunas are now so far known as to admit of their general features being set forth in a text-book, and also so far unknown as to offer a marvellous field for exploration to those possessed of such a guide. The appearance of this volume, which is intended both for university students and for amateur naturalists, is well timed, and it should cause a large expansion of local study. A full and lucid account is given of the general structure of insects, and the modifications char- acterising the twenty-four orders in which they are classed, illustrated by numerous clear and excellent drawings. This, the most important part of the work, is also the best, and can be recommended to entomological students of any country; the fundamental details of the wing-neuration in particular are thoroughly explained. The broad lines of the scheme of classification employed are reasonable and intelligible. The characters of the orders are tabulated in the form of a general conspectus, and in each order the analysis is carried down to families by dichotomous keys; hence an unassisted student should find himself able to refer any insect to its proper family. This method of procedure so much assists comprehension and saves so much time that it is unavoidable; but all who use such keys should be made aware that they can only be generally and not absolutely correct; exceptions are continually being discovered, and nothing in Nature is constant. Undoubtedly learners, especially when dull, like to have cut - and - dried formuhe, but they had better face the truth. They will also find that reliance on any single character is always risky, and that affinities must be judged by the sum of all characters, if they are to be natural.When we examine the internal arrangement of the orders, some errors are perceptible. Taking the Lepidoptera as an example, the butterflies are still classed as a separate division, Rhopalocera, equivalent in value to all the rest of the order except the primitive Jugata (Comstock's group, quite unnecessarily renamed by Dr. Tillyard T{omoneura), though the case ir really given away on p. 45, where the probable relationship to the Pyraloid groups is admitted. The definitely conclusive argument is, however, that when all other groups are considered separately, all are found alike impossible as ancestors of the butterflies, except the Pyraloids alone. Most authorities would also probably now admit that the skippers (Hesperiada) are not really from the same stock as the other butterflies, but from a related and more primitive one, the antennal club and loss of frenulum being adaptive characters and developed independently in each case. Again, the small jugal lobe quite correctly mentioned as present in early forms of Nepticulida (discovered by Miss Braun) might have warned the author that these highly interesting little insects (with quite unique neuration) cannot possibly be degraded Tineoids; they are an original development from Micropterygida , and must form a separate primary division; their universal distribution is part of their antiquity. The singular little Epipyropida, confined to Australia, the larva of which are parasitic on Hemiptera, cannot be included among the Tineoidea; the neuration, absence of palpi and tibial spurs, and all other characters refer them to the Psychoidea, certain forms of which they closely resemble. Nor does the inclusion of the Drepanida in the Noctuoidea seem to have any other merit than that of novelty; the type of neuration approximates to the Pyraloid. Under each family are given some few details of striking or interesting species, and there are coloured and plain plates acquainting the student with the general aspect of many of these, which are probably intended to stimulate popular interest. These items of general information appear some- times untrustworthy. Corrections under the Lepidoptera should be made as follows: Tinea fuscipunctella is not a clothes-moth, but a refuse- feeder; the similar clothes-moth is T. pellionella. Ephestia cautella is certainly not identical with E. kuehniella, the so-called Mediterranean Flour- moth'; it is the species formerly known as cahiritella Guen. The attribution of Lysiphragma to the Elachistide, even in the wide sense (out-of date) in which this term is used, is quite unintelli gible and cannot be intended; it is a true Tineid. The decaying family Copromorphida are twicestated to be confined to Australia and New Zealand; but even the first species ever described was from Fiji, and others have been recorded from the Papuan and Malayan regions, India, S. Africa, and 5. America. The character by which this family is separated from several others in the key (presence of cubital pecten in hindwings) fails to operate, as the same structure occurs fairly frequently in one of them, the Gelechiada, for example in Dichomeris. It may also be noted that the characteristic compression of the third segment (erminal joint) of palpi in Glyphipterygithe is not lateral but transverse.It is gratifying that Dr. Tillyard has attempted to preserve orthography in nomenclature. Such forms, however, as Sericostomatida, SelidoseJ matida (formed from Sericostoma, Selidosema), are really new errors, based upon the old error (corrected in NATURE, vol. 41, p. 342; 1890) that such generic names are neuter substantives, whereas they are feminine adjectives; the stem of the Greek stoma is stomat-, but of Sericostoma it is Sericostom- . Another barbarism adopted from Hampson is that of the use of the terms Trifin and Quadrifin for the divisions of the Noctuoids called by Guen e quite correctly Trifid and Quadrifida3; presumably on the supposition that -idce is a family termination and therefore inappropriate, whereas -id- is of course part of the stem (fid-, denoting fission), nd if the termination -ince is desired, the correct terms would be Trifidirue and Quadrifidina. Finally, in an interesting chapter on the geological history, Dr. Tillyard states his views on the origin of these two faunas. It is impossible to discus them here; a long article would be required even to recite the difficulties that arise on their consideration. Why, for example, if both New Zealand and Tasmania were successively connected with Antarctica, should there be fifty species of Crambus (the origin of which must certainly have been thence) in New Zealand and none in Tasmania? More probably Tasmania was never so connected. We must leave such problems to be investigated by some of the philosophers who are to he called forth by this useful volume.

ISSN:0028-0836    

DOI:10.1038/120720a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

(1) MR. R. S. HORSFALL and Mr. L. G. Lawrie, who are members of the staff of the British Dyestuffs Corporation, Ltd., the former being head of the dyehouse department of that firm, are peculiarly well-fitted for the compilation of a book dealing with the dyeing of textile fibres in general. The outlook of the average dyer must be limited largely to the activities within his own dyehouse, so that the types of dyeing upon which he is engaged and in which he is expert eventually become in his eyes the most important. As a result, although fitted to produce a specialised monograph dealing with the sections of the trade upon which he is engaged, lie wou[d be liable to produce an unevenly balanced general book on dyeing. On the other hand, nowhere can such a varied experience of dyeing be gained as in the dyehouse section of a works where colouring matters are manufactured. It is here that colour- ing matters are submitted to the most rigorous examination in order to discover their good qualities or defects, and to elaborate the most suitable methods of application in the case of products of commercial value. Further, the success of a colour works depends to a great extent upon close touch being maintained between the expert staff of its dyehouse section and all types of the colour consuming industries, Consequently, a most varied and evenly balanced experience of dyeing is gained, as is apparent in the book under review. The authors consider that most text-books attach more importance to dyestuffs than to the material to be dyed, with the result that the subject of dyeing the various fibres, cotton, bast fibres, artificial silk, wool, and natural silks, is approached through descriptions of the various classes of colouring matters. They have decided, therefore, to approach the subject from the angle of the material to be dyed, keeping in mind the manufacturing processes which the dyed material still has to undergo or the final uses to which it is to be put, with the view of simplifying the matter. Whether it is really a simplification to give excellent descriptions of machines without a single illustration, and to restrict the use of the formula of dye- stuffs to the solitary example of aniline black, is open to debate, but that the authors have produced an outstanding book on dyeing cannot be questioned It is written most attractively, and once its pages are opened it is difficult to lay it down unread. This thoroughly up-to-date book invites perusal and will be heartily welcomed by students of dyeing, whilst the general science reader who desires to know something of the science and art of dyeing as practised at present, can turn to no better source of information.(2) Mr. A. J. Hall, on the other hand, has laid himself open to criticism in attempting to revise Mr. Franklin Beech's book, The first edition, published in 1901, described various processes and operations involved in dyeing cotton fabrics, from a practical and empirical point of view, rather than a scientific one, and may have been of service to evening students in technical schools at that date. Actually, the limited and unsatisfactory revision which has been carried out has altered the original character but little, whereas such drastic treatment as to render the original text unrecognisable would have been necessary to convert this into a modern text-book. The publishers would be well advised to discard this book and arrange with Mr. Hall to write a new one. (3) Mr. David Paterson's well-known little book on colour mixing, in which he deals with his subject in a simple and practical manner, has proved a useful manual for elementary students since it first appeared in 1900. Although the original style has been preserved, the opportunity has been taken to revise the text somewhat without materially affecting its length. The dyed patterns used as illustrations of the text were dyed with German dyes in the first two editions, but are now dyed with colours of British manufacture, whilst further signs of the times are the increase in the price from 7s. 6d to 12s. Gd. since the second edition appeared in 1915, and the use of fewer coloured plates. Those engaged in the application of colouring matters cannot afford to neglect the subject of colour from a purely physical point of view, The first few chapters give an elementary account of colour, absorption spectra, and the spectroscope, and with this as a basis the remainder of the book deals practically with the mixing of lights, dyes, and pigments.Although it is true that skill in dyeing and colour mixing cannot be acquired from books alone, knowledge such as can be acquired from the first and third of the books on this list is indispensable if young men are to cope with present-day conditions in the colour-using industries.

ISSN:0028-0836    

DOI:10.1038/120721a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

ANY considerable work dealing with the selection, culture, and manuring of sugar-beet is certain to arouse interest in England, now that our own sugar-growing industry is developing with such great speed. In some six years our area under the crop has increased from about 8000 to 126,000 acres, and even those farmers who have been growing it since the starting of the Cantly factory in 1910 must confess to a considerable ignorance of the principles underlying the cultivation and manuring of it. Recently, many inquiries on the subject have been addressed to the various centres of agricultural teaching and research, and there has been some difficulty in obtaining trustworthy . Dr. Roemer, with a full century of continental experience behind him, attacks the whole subject in a patient and thorough mannei and quotes the chapter and verse of laboratory and field experiments in support of most of his statements and recommendations.In the department of manuring he owes much to Schneidewind, several of whose opinions and experiments he quotes, while in the realm of cultivation he has drawn on the work of Wollny and a host of other continental workers. In the matter of manuring, Dr. Roemer stresses the fact that an excess of nitrogen and its late application leads to poverty of sugar content, delayed maturity and poor keeping quality, points which were well confirmed in an experiment at Rothamsted carried out only last year. In other particulars of manuring he recommends a moderate use of phosphate to ensure good texture in the root and to help maturity, and he thinks that a shortage of available potash leads certainly to a lowering of the sugar percentage in the root. In regard to spacing the roots in the field, Dr. Roemer favours a wider setting of the rows than most continental experts. 20 in. x 9 in. is the actual spacing that he names, and this compares curiously with the 14 in. x 8 in. and 16 in. x 8 in. which have been recommended by many of the Dutch and German experts. Many British growers have objected to these very small spacings on the ground that it is practically impossible to use horse labour in the narrow rows, and that addftional hand labour is very expensive and slow even when it is available. It is interesting to observe that Dr. Roemer supports his practical recommendation with a similar statement of labour difficulties in Germany. Throughout the book he makes great play with the necessity that exists for improved mechanisation in the handling of the crop in the interests of speed and labour saving, and he has a number of inter " esting things to say about spacing drills, singling machines, and mechanical harvesters. In this last and very important particular he considers that the problem of mechanical harvesting of beet is now solved, and that we only wait for improvements of the existing machines.Taking the book on the whole, it appears as a very valuable addition to a section of agricultural literature which is not well represented in Great Britain, and it seems reasonable to expect that many of Dr. Roemer's conclusions will apply quite closely to sugar-beet growing iii British conditions.

ISSN:0028-0836    

DOI:10.1038/120722a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

A BOOK verging on 900 pages provides scope for much matter, and the designation "Handbook" rather inadequately describes the wealth of information which is to be found in the volume before us. Although bearing the names of two authors, it is really a compendium by them and nine other contributors, covering in its thirtyfive chapters almost every subject and topic connected with hydro-electric development works. It is essentially an engineering manual, based on the wide field of experience obtainable in North America, where water power is an important natural endowment and is being exploited for industrial purposes on a scale of magnitude greatly exceeding anything that is feasible in Great Britain. The mere enumeration of chapter headings would occupy almost the whMe of the space avail- able for a short notice, and it is ozily possible to indicate a few of the more important items which are treated by the various writers. There is an introductory section on rainfall, evaporation, and run-off, illustrated from United States records, together with a description of methods of estimat. ing stream and flood flow, with the resultant yield of data respecting storage and power available for development. A short r sum of principles of hydraulics is then followed by four chapters dealing with different types of dams, and thereafter come descriptions of various other constructional features and power-developing equipment, including turbines and generators, extending to power transmission lines.In brief, the book is a very complete and concise summary, from the American viewpoint, of the theory and practice of water-power supply at the present day. It is excellently printed and pro- duced. The diagrams also are clear, and in some instances are duplicated, so that one copy may be detached for pocket use.

ISSN:0028-0836    

DOI:10.1038/120723b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

FOR the layman who can read German, and is not deterred by Germanic characters, Dr. Hauser has provided an extremely interesting survey of early human types and history. The introductory chapters include a brief summary of historical geology and of the evolution of life forms. Considerable attention is given to the Wegener hypothesis of continental drift, the treatment leading up to a discussion of the new world' of the Tertiary period and the acceleration of progress in the world of life that accompanied the far-reaching geographical changes of the time. The next revolutionary event was the onset of widespread glacia tion that began a new period and saw the effective beginnings of mankind. In dealing with Pakeolithic man, Dr. Hauser is thoroughly up-to-date, for he appears to have made use of all the evidence available up to the middle of 1926. He is particularly interested in the art and culture of early man, and by plotting the localities of significant discoveries he attempts to follow up the migrations of some of the recognised races. The book is beautifully printed and illustrated, and is a thoughtful contribution to the literature of its subject.

ISSN:0028-0836    

DOI:10.1038/120724c0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN a recent paper on the optical excitation of mercury vapour (Phil. Mag., Sept. 1927) I directed attention to the fact that lines excited by two successive processes of absorption should increase with the square of the intensity of the exciting light, while lines resulting from a three-stage absorption should increase with the cube of this intensity.As an example of the last case, we may take the emission of the line X3650 of mercury. The vapour of mercury at room temperature in a quartz tube, highly exhausted, is illuminated by the total radiation of a water-cooled quartz mercury arc. The absorption of the line X2537 raises the electrons from 18 to 2P2' from which level they are raised to is by the absorption of X4358. From is some fall to 2Pi' a metastable level, with emission of X5461, and from here some are raised to the d level by the absorption of X3650, from which level they return to 2p1 with emission of X3650. If we move the arc away until the illumination vf the vapour is reduced to one-half of its initial value, one would expect that the intensity of ,X2537 would be reduced to one-half, of X4358 and X5461 to one- quarter, and of X3650 to one - eighth of their initial values, for by reducing the illumination by one-half we have only half as many electrons raised from 18 to 2P2' owing to the reduced intensity of X2537. But k4358 has been reduced by one -half as well, consequently there is but half as much light available for absorption by the reduce* number of electrons in 2P2 Lines resulting from a two-stage absorption process are thus reduced to one-quarter, and from a three - stage absorption to one - eightth of their initial values. Several observations bearing out this view were given, though a special investigation of the matter had not been made at the time. Practically all of the light emitted by the tube results from two-stage or three-stage absorption. This accounts for something that has always surprised me, namely, the impossibility of obtaining a satisfactory amount of emission by forming an image of the lamp on the resonance tube by means of quartz lenses. I had attributed it the absorption of A2537 by mercury vapour in the air, but the relations above described amply account for it.The phenomenon can be shown in a very spectacular manner by the very simple expedient of inserting a sheet of fine wire gauze, which is non-selective in reducing the intensities of the lines, first between the resonance tube and the eye, and then between the lamp and the resonance tube. We find that in the latter case the intensity of the emitted light is very much fainter than when the gauze is held between the ye and the tube. The gauze employed was of very fine copper wire, and transmitted about one - fifth of the light. When held between the eye and tube, the light was reduced to one-fifth, but when held between the lamp and the tube, the reduction was to one twenty-fifth; i.e. the light was almost invisible. A quantitative investigation of these relations is now in progress in collaboration with E. Gaviola.

ISSN:0028-0836    

DOI:10.1038/120725a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

CLERK MAXWELL many years ago surmised that viscous liquids in a state of flow should exhibit birefringence, and devised methods of observing the phenomenon. Vorländer and Walter (Zeits. Phys. Chem., 118, 1; 1925) have recently investigated no fewer than 172 liquids of known chemical composition by Maxwell's method, and their work has demonstrated conclusively that a great many pure liquids which cannot by any stretch of language be classed as colloids, exhibit birefringence when subjected to viscous flow. The Maxwell effect, as it may be called is thus a characteristic property of pure liquids just as much as the power of exhibiting birefringence in strong electrostatic or magnetic fields. We wish briefly in this note to indicate a molecular theory of the Maxwell effect we have worked out which has proved itself very successful in explaining the observed phenomena.It is easily seen that the stresses in flowing liquid can be considered as equivalent to a set of tensions and a set of pressures acting perpendicularly to each other, and at angles of 45° to the plane of sliding. When the liquid consists of molecules which are highly asymmetric in shape, there would be a tendency for the molecules to orientate under the influence of this system of stresses in such manner that the longest dimension of a molecule tends to lie along the axis of tensions and the shortest one along that of pressures; because such orientation would evidently result in the fluid, regarded as a densely packed assemblage of molecules, expanding along the direction of tensions and contracting along the direction of pressures. thus allowing the system of stresses to do work. By consiclering the work done during such deformation by the acting stresses as equivalent to the change of energy of the molecules resulting from orientation under a system of couples acting upon them, we can determine the latter in terms of the viscous forces and the asymmetry of shape of the molecules; it being remembered that the orientation is opposed by the thermal agitation of the fluid and that the resulting equilibrium is to be determined statistically in accord- ance with the Boltzmann principle. The birefringence of the fluid resulting from the orientation of the molecules under the viscous stresses and their known optical anisotropy, is then readily worked out on lines analogous to those used by Langevin in his theory of electric and magnetic double refraction. The final expression obtained in this way for the difference between the refractive indices n and n2 for the vibrations along the axes of tensions and pressures respectively, is:(n2 1)(n2+2) flt fl 5nvkT(a1a2)(b1b2)+(a2a3)(b2b3)+(a3a1)(b3b1) v . (a1+a2+a3)(b1+b2+b3)where n is the mean refractive index of the fluid, is the number of molecules per unit volume, k is the Boltzmann constant, T is the absolute temperature, a1, a2, a3 are the linear dimensions of the molecule along the three principal axes, b1, b2, b3 are the optical moments induced in the molecule along these axes by unit field acting on it successively along the same three directions, is the coefficient of viscosity and v/c is the velocity gradient. The birefringence calculated from our formula, utilising the optical anisotropy ascertained from observations on light scattering and the geometrical dimensions derived from X-ray data, comes out in excellent agreement with the determinations of Vorlnder and Walter.The extension of the theory to the case of colloidal solutions and gels is at present engaging our attentio

ISSN:0028-0836    

DOI:10.1038/120726a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE letter in NATURE of Oct. 8, p. 510, from Prof.R. W. Wood and Mr. Loomis directs attention to the possibility of developing spectra by means of high frequency oscillations. Work on these lines has been proceeding in this department for some time, and the results obtained with mercury as a ‘trial horse’ are encouraging.A short coil of copper tubing was wound round a horizontal hard glass tube through which a stream of mercury vapour was caused to flow. The coil was connected in parallel with a condenser, and oscillations were maintained in this circuit by means of a high- power three-electrode valve. The frequency of these oscillations was of the order of 106 cycles per second, the voltage applied to the circuit could be varied from 2000 to 10,000 volts, and the power input increased up to 35 kilowatts. The pressure inside the glass tube was adjustable by the admission of air, and the spectrum produced when the coil was activated was examined end-on by means of a quartz spectrograph. Before a glow was visible, the resonance line X25367 was photographed with a long exposure. An increase of the voltage applied to the circuit caused the appearance of a greenish glow, which was found to be due to the lines of the s and d triplet series in addition to this line; prolonging the exposure only resulted in more members of these series being recorded. A further increase in the voltage caused the colour of the glow to change to that of the ordinary mercury arc, the photographs now showing the resonance line, the s and d triplets, the lines of the S and D singlet series, and some combination lines. Only those combination lines were present, however, which involved the arrival and departure levels of the series lines present. When the voltage was still further increased, more members of the triplet and singlet series were developed, together with additional combination lines connected with these new members.Simultaneously excited, however, were also thirteen lines, which have not yet been allocated to any series or combination, though these have all been identified as being present in the ordinary mercury arc. Their wave-lengths were 39841, 38604, 38206, 37904, 37518, 35615, 35437, 33905, 33515, 28200, 26867, 2660 1, and 25404. They were all of very feeble intensity except the first, which was as strong as an early member of the triplet sehes. A step by step reduction of the pressure from 1 cm. to that of the vapour alone, keeping the voltage constant, produced the same effects as increasing the voltage when the pressure was constant. An increase in the tempera- ture of the vapour also facilitated the development of the lines. The line X3984 1 was abnormally affected by pressure; increasing the pressure caused it to fade much more rapidly than the other lines. It. had been anticipated that enhanced lines due to atoms in various stages of ionisation might have been obtained, especially near the circumference of the tube, but these have not yet been observed; further endeavours to obtain them will be made. It is remarkable that although several of the lines of the p series are present in the ordinary arc with an intensity as great as that of some of the higher members of the s and d series, yet they have not been observed as being excited by this method, even when the exposure has been prolonged up to five hours. It is possible that they require higher voltages for their excitation than have been available so far.It is apparent that this method of developing spectra is full of promise, and its extension to other elements than mercury, the spectra of which have not yet been analysed so completely, is proceed

ISSN:0028-0836    

DOI:10.1038/120727a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature