摘要:

THE printed chronicle of human endeavour in Tall civilised countries of the world, in many tongues and recorded in multifarious publications, has long been accumulating at a rate so great, that not merely is its co-ordination beyond the power of any single mind, but also no central institution has been able to analyse it, so that this priceless store of knowledge may be made available for further advance. At an earlier period, the author of a scientific or technical paper may have cherished the fancy that, by publishing his work, he was giving it to the world. To-day we have learnt by experience that to print a magazine article may be merely adding padding to a volume on the library shelf, for, without an index to recorded information, it is likely to become inaccessible. Nearly every one of that comparatively small band of workers who are patiently seeking to extend the boundaries of knowledge, to discover new and better methods of manufacture, or to invent and improve apparatus and machinery, must have realised the continual duplication of effort, which acts as an ever-present check to progress.The lack of an extensive index to information was felt during the War; then machinery was hastily invented and methods of manufacture quickly devised, while the records of better apparatus and processes were lying buried on the library shelves. It is agreed that in peace and war a comprehensive guide to recorded knowledge would be an asset of the greatest value that would lead at once to important scientific and technical developments, while without it untold time and energy are being wasted throughout the world by the useless repetition of research and invention. Various attempts have been made from time to time to collect, classify, and distribute information. A large number of publications are, or have been, devoted to the bibliography of special subjects; perhaps the greatest of all was the International Catalogue of Scientific Literature. There are, besides, many bureaux, both English and foreign, of divers types, engaged in the preparation of indexes to particular classes of information. Yet, in spite of all this activity, not the semblance of the desired key to knowledge is available.This deplorable failure, which is restricting progress and prolonging unnecessary discomfort and inconvenience, may be due in great part to the lack of that which it is the purpose of bibliographies to supply; that is, information. For want of knowledge, bibliographical research is being undertaken everywhere, at home and abroad, without attention to the canons of bibliography or previous experience of its methods. Each abstracting or indexing body adopts a different system of classification and the abstracts or index slips are produced without regard to size, so that they cannot be mounted on cards and amalgamated with other bibliographies, and the information collected becomes hopelessly lost in thousands of separate parts. Moreover, every bureau indexes or abstracts papers that are done by, usually, a number of other bureaux, and only a fraction of the literature is covered. The science of bibliography is not a subject of general study, and many scientific workers who realise the need ofpractical training in scientific method as well as knowledge of previous work appertaining to their special field of investigation, fail to understand that the same is true of bibliography. The would-be bibliographer must bring a scientific mind to the study of his task and must gain proficiency in bibliography by laborious practice. The indexing of scientific papers has also the added difficulty that the needs of scientific workers cannot be appreciated fully except by themselves. Thus an efficient index to scientific literature can scarcely be produced except by the application of a thorough knowledge of bibliographical science, wide experience in its application, and expert knowledge of the subjects indexed; that is to say, it is imperative that the scientific method be applied to bibliography.Since the preparation of a complete index to published information involves the co-operation of many workers, it is necessary that a single system of classification should be chosen, which must be kept up-to-date by some central body. If, however, a definite classification were accepted and utilised by existing bibliographical undertakings, it would be possible to amalgamate their work into one series of cards which would go far towards the universal index desired. All information collected on a given subject would then fall together into one place to be available at need, and it would become apparent that identical information is being collected from the same periodicals by many different indexing agencies, and that information on a given subject is interesting to workers in many different branches of science or technology. By consultation, overlapping could be avoided, and energy, at present being wasted, could be used in indexing literature not dealt with hitherto. The International Classification, described by Dr. S. C. Bradford elsewhere in this issue, is, ready to hand, such a scheme as is required for the preparation of a great index to recorded information, and no other suitable system is available. The general adoption of this code would make possible now the realisation of the index desired. Some thousands of bibliographies are in actual progress. At present their utility is very limited. But merely to number the bibliographical titles by the International Classification would make it possible to amalgamate them all into one index of the greatest value to mankind. The scheme has been utilised on the Continent as the basis of extensive bibliographies. The Classification is surely gaining ground and has received the support of the League of Nations. Recently, in Great Britain, the Optical Society has published an English translation of part of the Classification which has been used for the classification of the index to its Transactions. This can now be cut up, pasted on cards, and incorporated with other bibliographies numbered in accordance with the code.When the International Catalogue of Scientific Literature came to an end, it was obvious that sooner or later the preparation of a comprehensive guide to scientific literature would have to be revived. The ideal solution to the problem has been suggested to be the building up of a National Science Library to take every important scientific periodical or publication together with a complete index to their contents, so that documentary research could be carried out in one building without waste of time journeying to different libraries. As the Science Library at South Kensington contains an exceptionally extensive collection of scientific periodical literature, it seemed desirable that its resources should be developed so as to ascertain the possibility of realising such an ideal library. An organised effort is being made to augment the fine collection of scientific journals and transactions in the Library so as to make it as complete as possible. This has been so successful that periodicals are being added at the rate of a thousand or more a year, and the Library now includes between six and seven thousand of the items in the World List. The continuation of this undertaking, if possible on a somewhat larger scale, should lead in a few years to the gathering in the Library of a nearly complete collection of scientific periodicals. After very careful consideration, the International Classification has been adopted in the Science Library for index ng the titles of its books and more important papers. The Library contains also sets of certain other bibliographies, as well as of some smaller undertakings based on the same system. All these are now being collected into one repertory, to which it will be possible to add any bibliographies that adopt this classification afterwards. The whole will be available for consultation in the Library together with the books, or from the index it should be possible to supply extracts by post at the cost of typing and postage. The work of the past three years shows that the attainment of the first half of the ideal is possible. Its complete realisation would follow if it were possible for bibliographical undertakings generally to adopt the Decimal Classification of the Brussels Institute.

ISSN:0028-0836    

DOI:10.1038/119417a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

(1) THAT the Rutherford-Bohr atomic model, T despite its remarkable success in explaining and correlating so many of the facts of physical and chemical science, is not yet universally accepted, is evident from a study of the first of these three books, the title of which will probably lead many who are unfamiliar with Dr. Crehore's writings to expect something quite different from what they will find. The book is really an account of the progress of the author's own particular atomic theory. Although we fancy that it will win few converts to his views, it is, nevertheless, not without interest. Broadly speaking, Dr. Crehore believes, as so many of us would like to believe, that all atomic processes can be explained in terms of classical electrodynamics. It will probably be in the earlier chapters that the work will prove least convincing. Here the author describes the atomic models on which his subsequent calculations are based. We are told that the hydrogen atom consists of a nuclear charge of two units with two spheroidal electrons in contact with it, one on each side: similarly, the helium atom has a positive charge of four units, and on each side of this charge are two electrons closely bound to it. From these two fundamental atoms Dr. Crehore proceeds to construct the more complex atoms bv a suitable arrangement of hydrogens, heliums, and cementing electrons. His atoms are more or less closepacked assemblages the linear dimensions of which are of the order of 10-13 cm.The difficulties presented by such atoms are manifold, but if once the reader gets past these early chapters and accepts, even if only for the sake of argument, the hypotheses, he will find the subsequent chapters more logical. Indeed, in the development of his theory, Dr. Crehore shows no small courage and considerable mathematical skill in dealing on classical lines with these unconventional atoms. Perhaps the most interesting problem he sets himself is to explain why it is that atoms so small as 10-13 cm. should build themselves into solids in which they are separated by distances some ten thousand times greater than this. For this problem he claims a solution in the case of hydrogen. The origin of a spectrum line of wave-length A involves, according to this theory, an excursion of an electron to a distance 0-05X. This applies equally to the optical and X-ray regions. In considering the latter spectra, the author emphasises the fact that this excursion is small compared with atomic distances in the solid. It is of interest to note, however, that recent direct determinations of long wave-length X-radiations would involve excursions considerably greater than the distance of closest approach of neighbouring atoms. In spite of a bold defence of these atoms, which includes an explanation, based on them, of gravitation, there are still many gaps which will have to be filled and many difficulties which must be overcome before the majority of physicists will consider that the theory has progressed sufficiently far to replace that which is more or less generally accepted.(2) If a course of Dr. Crehore has shaken, ever so slightly, the reader's faith in the conventional atom of to-day, it should be easy to restore it by a study of the second of these books. Dr. Haas is well known as a writer with a very considerable gift for clear and concise exposition, and this latest work worthily upholds this reputation. It is based on a course of lectures intended for a nonspecialist audience and covers practically the whole range of modern atomic physics. That is a great deal to expect of a relatively small volume, but the author has selected his material with excellent judgment and woven it together into a convincing narrative. There is no need to enter into the details of his presentation of the subject; suffice to say that he shows us that, whether we approach the problem of atomic structure from the point of view of optical spectra, X-ray phenomena, radioactivity, or any of the other lines, we are led to similar conclusions and to similar conceptions as to the nature of the atom. If any one offers criticisms it will probably be the specialist, who may feel that the whole subject, as here presented, seems too simple, the interpretation of the facts too straightforward, the structure of the atom too obvious. This is a criticism which most authors will welcome. Too often a book which is perfectly sound from a scientific point of view is a very poor product when judged from a literary or artistic viewpoint, but Dr. Haas deserves our congratulations and gratitude for having written an account which is not only an up-to-date expression of the situation but also, above all, one which is readable.(3) The third volume, by Dr. Gianfranceschi, is of a different type again. It is intended for the student rather than for the general scientific reader. As the title suggests, the author is concerned rather with the development of the electrical theory of matter than with the details of atomic structure. After preliminary chapters dealing with the basis of modern views of the structure of matter, he gives an outline of the kinetic theory of gases and its application to the theory of electrons. This naturally leads to a discussion of the problems connected with the passage of electricity through metals and kindred phenomena. Following the historical development, the author introduces the quantum by a short account of black-body radiation, and then proceeds to a brief description of modern theories of atomio structure and optical and X-ray spectra. It might be expected' that such a book would be full of somewhat abstruse mathematical analysis, but Dr. Gianfranceschi has succeeded in presenting his subject with the help of only such mathematics as every serious student of modern physics and chemistry may be assumed to possess. It is essentially a theoretical work, and experimental methods and results are introduced only in so far as they provide a basis for the theoretical discussion or a verification of the predictions of the theory. The fact that the book is now in its third edition is sufficient recommendation and sufficient proof that it has already proved its usefulness to a wide circle: without doubt, this new edition will be as popular as its predecessors.

ISSN:0028-0836    

DOI:10.1038/119419a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

(1) THIS volume completes the second edition of the well-known monograph upon the endocrine organs issued for the first time in 1916 and founded on a course of lectures (Lane Medical Lectures) delivered by Sir E. Sharpey-Schafer at Stanford University, California, in the summer of 1913. The second edition, in two volumes, has greatly outgrown its predecessor, and the second volume is the larger of the two, more than half of its bulk being devoted to the pituitary body. The other endocrine organs treated in it are: the pineal body, the duodenal and gastric mucous membranes in their relation to the production of secretin and gastrin respectively, the islets of Langerhans of the pancreas and the sex glands, including the interstitial cells of the testis, the ovary, and corpus luteum. The histology of these organs is detailed and their structure illustrated by numerous drawings and photo-micrographs, all admirably selected and reproduced. Development of the organ is described in the case of the pituitary body, where its consideration is essential to a proper understanding of its differentiation with regard both to structure and physiological properties. The chemistry of the active principles produced by the organs and the history of the attempts to isolate them are recorded in so far as trustworthy evidence is forthcoming. Much, however, remains to be investigated in respect to the chemistry of the internal secretions, and the threshold of this subject has barely been reached as yet.The physiological action of extracts of the organs, illustrated by admirable graphic records, and the history of their discovery, are fully detailed. The references to authors cited are exhaustive, and are given in foot-notes on the pages on which they are quoted, the value of the work being thereby greatly enhanced. Clinical evidence bearing upon the effects of increase and decrease of activity of the organs has been wisely selected. The physician will find the book an invaluable one as an authoritative guide to the proper appreciation of what results may and may not be legitimately expected from the use of preparations of the endocrine organs as remedies. Unfortunately, the autacoids or self remedies secreted by the endocrine organs do not lend themselves in all cases to a relatively simple method of employment such as is illustrated by the active principle of the thyroid.The importance of the endocrine organs in physiology and medicine has long been established, but the grain is apt to be missed in the chaff, so abundant and varying in value is the literature of the subject. No one is better qualified than Sir E. Sharpey-Schafer to undertake the sifting required, and in these two volumes he has succeeded beyond praise in producing a standard work upon endocrinology which will be indispensable to the research worker and welcome to the physiologist and practising physician alike. (2) This monograph, profusely illustrated by drawings in the text, and by special plates of photo-micrographs and one of coloured drawings, deals entirely with the morphology, histology, and embryology of the pituitary body. The various classes of vertebrates are considered, and in the concluding chapters the homologies of the gland are summarised, a scheme drawn up of its evolution, and observations made upon the types best fitted for experimental purposes.The opening chapter gives an indication of the methods of preparation employed by the author. No mention is made of Flemming's solution, which, in the reviewer's experience, is by far the best fixative for the pituitary body, but requires a special technique in the subsequent procedure of staining. The author has entirely missed the histological evidence of secretory material in the pars nervosa, although it can be demonstrated in abundance in all types of vertebrates in which extracts of the posterior lobe yield an active pressor material. Harvey Cushing (Cameron Lectures, 1925) has indicated the importance of this material in the human pituitary, and has commented upon the surprising way in which it is ignored by many histologists. Few references to the literature of the subject are made in the text, and the reader will find it impossible to distinguish between the original observations of the author and what has already been noted by others. This is a serious fault, and deprives the book of much of its value as a basis for further workers. An appendix gives a bibliography of works upon the pituitary published since 1913.Most of the illustrations are original. The drawings are helpful, but references to them in the text are not always accurate; e.g. on p. 12 the reader is referred to Fig. 28 for an illustration of variations in the Golgi apparatus of the cells of the pars anterior of the mammalian pituitary, and on turning over a number of pages finds a line diagram of a transverse section of a fowl's pituitary. The photo-micrographs are far too crowded, and although well reproduced, lose in value because of their arrangement and the absence of an adjacent description. To turn from criticism, it must be admitted that the author has recorded much work that is praiseworthy. Methods have been devised which appear to enable a differentiation to be made between pars intermedia and pars tuberalis. He has much to say that is interesting although one may not always agree with it, and his views upon the homologies and evolution of the gland cannot be lightly dismissed.

ISSN:0028-0836    

DOI:10.1038/119420a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

PROF. DALY of Harvard once again has pre-sented in book form matter of geological interest gathered from all parts of the world, and has supplied the desirable connective tissue of theory and speculation. The present work is based upon a course of popular lectures given at the Lowell Institute of Boston. Below the surface, however, it is easy to realise that it has been prepared for the serious student as well as for his lay brother. There is something of the fascination of Lyell's " Principles " in these traveller's tales, each one with its moral; and the suggested references listed chapter by chapter at the end of the volume will be found most useful. The 187 illustrations, too, are excellent; and an author's note invites their reproduction except where covered by previous copyright. To begin with, we are introduced to earthquakes, with proper emphasis on their scientific importance as well as their frightfulness-fewer people are now killed by earthquakes than by motors. The localisation of earthquakes in the Tertiary mountain belts is explained as a result of up-and-down and sideways adjustments of already folded masses. Observed surface displacements are discussed with copious illustration. In passing, one may perhaps protest against ring-cracks being referred, in Fig. 10, to " torsion of the ground." These particular cracks are surely analogous to countless ringfractures that a few years ago used to develop through settlement in relation to old shell-craters in Flanders. But to return from this aside, Daly not only illustrates surface faulting in connexion with the 1906 San Francisco earthquake, but also shows how the final snap was preceded by a more distributed distortion that has been traced in observations of the U.S. Coast and Geodetic Survey.Daly next explains seismograms and the three kinds of earthquake waves distinguishable in these records. We are now getting to the heart of the subject. Advancing the usual arguments, our author claims that the continents are great discontinuous masses of aggregate granitic composition, and that they float in iceberg fashion with foundations immersed in crystalline basalt. He further suggests that below the crystalline basalt is a circum-mundane layer of glassy basalt, in which high temperature inhibits crystallisation. This conception has two important bearings upon volcanic and tectonic problems: it entails a limited inversion of the law of increasing density with increasing depth; and it also gives a higher subcrustal plasticity than might otherwise be expected. Probably many readers will hope that Daly will recast his theory to make his density inversion local as well as limited. A chapter naturally follows on volcanic action. It is a valuable resum6, with much stress laid on Kilauea in general and gas-fluxing in particular. St. Helena is also mentioned as a geological paradise, and regret is expressed that Napoleon did not realise his opportunities in this direction.An instructive attempt is made to disentangle earth and sea movement in comparatively recent phenomena of emergence and submergence. Jamieson's interpretation of isostatic earth-movement in connexion with ice-load is accepted as of prime importance for the understanding of the raised beaches of glaciated lands. On the other hand, a low raised beach, which Daly has traced along much of the shores of the Atlantic and Pacific Oceans, is attributed to a Neolithic withdrawal of water to augment some still existent icesheet. Similarly, Darwin's submersion theory of atolls is brought into relation with release of water during the wane of the glacial period. It would be interesting if some other isostatic expert were to approach Darwin's theory fortified with the apparently obvious assumption that all oceanic volcanic islands must in course of time subside. The mountains of the globe are divided by Daly fairly comfortably into Mid-latitude-Mediterranean and Circum-Pacific zones. The nature of mountain folding and thrusting is illustrated, inter alia, by Fig. 148 of an overthrust outlier, Chief Mountain, Montana. In scenic expression it rivals the best of the Swiss klippes. Daly's outlook upon mountain problems is naturally reminiscent of the writings of Dana, James Hall (of New York), and Dutton, but it has notably original features. Here we need only point out that Daly joins Osmond Fisher, Dutton, Taylor, Wegener, and many modern alpinists in revolt against the old earth-contraction theory of mountain origin. He adopts instead the continental drift hypothesis, and adds new features. In outline, his statement is as follows:(1) Continental drift is of the nature of a gigantic landslip-exceeding in scale the tectonic landslips envisaged by Schardt or Reyer. (2) A cause is suggested for the continental doming that is supposed to have preceded continental slipping.(3) The glassy substratum makes slipping easy. (4) The slipping continents crumple marginal geosynclines.(5) The glassy substratum allows of subsidence of crust-blocks beneath crumpling geosynclines, and the fusion and expansion of these blocks is responsible for eventual elevation of mountain chains. A feature which continually crops up in Daly's discussion of mountains is an assumed lag between crumpling and elevation. In Europe, however, the evidence distinctly favours contemporaneity of these two phenomena (with, of course, later repetitions of upheaval in response to erosion as explained by Fisher in 1881). For example, the Tertiary Flysch and Molasse of Switzerland derived most of their material from already elevated Alps that were actually travelling. The travel was so real that the Flysch was in due course entirely incorporated in the Alpine chain, and even the Molasse, though it formed later and farther north than the Flysch, now lies marginally overturned and over-ridden.

ISSN:0028-0836    

DOI:10.1038/119421a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN my letter dated Mar. 1, which appeared in NATURE of Mar. 12, p. 387, it was stated that the ‘forbidden’ line λ2270 appeared in the excited vapour in association with the band spectrum.I now find that the other 'forbidden' line at the computed position X2655 60 also occurs in the excited vapour, and much more strongly than X2270. The observed position of the line is X2655-73. This measurement might doubtless be improved upon, but the line is very definitely on the less refrangible side of the line X2655 13 in a comparison arc spectrum. The 'forbidden ' line is absent from the latter, and, so far as I know, it has not been observed before in any circumsta

ISSN:0028-0836    

DOI:10.1038/119423a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WHILE recognising the importance of the evidence brought forward by Dr. Lawson in NATURE of Feb. 19, p. 277, I cannot agree that it is sufficient to demonstrate that only an insignificant portion of the energy emitted by radio-active elements in rocks is expended in effecting changes in the surrounding minerals. He states that when such elements are placed in glass tubing, the energy absorbed in producing modifications in the glass does not amount to more than one per cent. of the total given off and is probably not more than about a tenth of this value. He infers that a similar state of things must prevail where biotite mica instead of glass is exposed to the radio-activity, and this in spite of the fact that on heating the pleochroic spheres (usually referred to as haloes) that result, they “ exhibit the phenomenon of thermo-luminescence,” but claims that “the energy so liberated does not produce catastrophic results, and is manifestly small.” The last statement is, to say the least, by no means obvious. The question at issue is simply quantitative, and it therefore seems to be dangerous to argue that because glass tubing containing about 70 per cent. of silica and a certain amount of lime and soda absorbs but a small proportion of the radio-active energy, this will also be the case with biotite containing, say, 38 per cent. of silica with smaller amounts of alumina, iron oxide, potash, and titanium oxide. That the alteration in the biotite caused by the radio-activity is very considerable follows from the fact that, as shown by Dr. Brammell of the Imperial College, the pleochroic spheres persist even when the biotite has been converted by pneumatolytic agencies into a substance practically identical with muscovite. He also found that it was necessary to keep biotite at a dull red heat for about six hours to render the ‘haloes’ invisible. During that time a very large amount of heat might be released without “ catastrophic results.”Recently, records have been published of a deep boring at Dubbeldevlei in the Cape Province of South Africa (about Lat. 300 30' S. and Long. 21° 35' E.), and they deserve consideration in connexion with this question. It reached a depth of approximately 5080 feet, and a survey by Prof. G. A. Watermeyer (Trans. Geol. Soc. S. Africa, vol. 26, pp. 65-7, 1924) showed that the depth could not be in error more than 0-3 of a foot. Temperature measurements were made by L. J. Krige and H. Pirow with the greatest care (ib. pp. 50-64). Down to 2137 feet the rocks consisted of horizontal Ecca and Dwyka beds, shales, with occasional dolerite sills, and tillite. Then came 550 feet referred to the Fish River Series, correlated with pre-Cambrian Pretoria Series. The remainder of the boring was in the ancient granites and gneiss which outcrop about fifty miles to the northward. They are widely extended in South Africa, not only at the surface but also below ground, as evidenced by fragments in the Kimberlite pipes (Du Toit, " Geology of South Africa, p. 44, 1926). They probably underlie all sediments except the primitive metamorphic rocks of pre-Witwatersrand age, into which they appear to be intrusive, and extend downwards for a depth of several miles at least. Being of acid composition they are presumably rich in radio-active substances. They must contain, too, a considerable amount of potassium, which Dr. Lawson claims as being radio-active. The average temperature gradient for the whole depth of the boring was 10 C. in 31 in., but varied from 10 in 18 3 in. to 10 in 518 in., mainly in accordance with the conductivity of the local rock. In the granite and gneiss, the conductivity of which lies between 0 005 and 0-006, the average gradient was 10 in 45 4 m. In shale the gradient was at its highest, 10 in 18 3 in., for the conductivity of shale is stated to be only 0 0023. In the Witwatersrand mines the gradient is so low as 10 C. in 112 8 in., the conductivity of vein-quartz and quartzite being 0 0095, and that of pure quartz more than twice as much. It is remarkable that the presence of extensive granite and gneiss in the lower 2400 feet of the bore, and for a far greater depth below, seems to have had no appreciable effect on the gradient. Unfortunately, no determination of the radio-activity of the rocks traversed appears to have been made. It is to be hoped that this will be carried out, as the cores are apparently

ISSN:0028-0836    

DOI:10.1038/119424a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN a discussion of the standardisation of hydrochloric acid with different standard substances (J. Amer. Chem. Soc., 70, 1772, 1926), I made the following remark: “After the substance [borax] had been dried at 200°, the crucible was placed in an electric oven at a temperature of 700–750°, until constant weight was attained. When afterwards it was heated at 800°, at which temperature the salt fuses, the weight did not change. We cannot confirm the statement of H. V. A. Briscoe, P. L. Robinson, and G. E. Stephenson (J. Chem. Soc., 122, 150, 1925), who state that fused borax loses sodium oxide. Even after the substance had been heated for two hours at 8000 the weight did not change.”Prof. Briscoe and P. L. Robinson (NATURE,118, 374, 1926), remark on this statement that the fact is well established that borax is volatile at high temperatures. They even were able to show in a qualitative way that fused borax is decomposed at higher temperatures. They say: " The inside of the silica muffle used for the fusions of borax in our investigation was completely coated with a white opaque enamel, about 0 06 inch thick, of a product of a reaction between the volatilised material and the silica." As there is such a discrepancy between Briscoe's and my own results, I repeated the latter, but again I found a negligible loss in weight after two hours' heating at 800°. Now Prof. Briscoe and his collaborators say they fused the borax in a platinum dish (large surface), in the electrically heated muffle in a current of air free from carbonic acid and dried over solid caustic potash. In total they heated it for 2-2k hours. Hence they worked under conditions very favourable for volatilisation. In my experiments the borax was heated in a covered platinum crucible (surface of the fused borax about 2-5 cm.), without passing a current of air over it.In order to check the results formerly obtained we heated about 3 gm. anhydrous borax in the electric oven under the same conditions as described. We continued the heating for about fifteen hours at 880°, and afterwards twenty hours at 9400. At different intervals the borax was weighed. (It is unnecessary to take precautions against hygroscopicity of the anhydrous salt, as the melt of borax with its small surface attracts water from the atmosphere very slowly. Even after standing in an open crucible overnight in the balance, the weight did not change.) From the results it appeared that the borax lost at 8800 0-16 mg. per hour, and at 9400 0-23 mg., due to the volatilisation. We must therefore confirm the statement of Briscoe and his collaborators, that fused borax is volatile. On the other hand, it is evident that under favourable conditions (heating in a crucible without passing over it a current of air, and at a temperature of about 8000) the loss due to the volatilisation of sodium oxide is so small that it is negligible, even for most accurate analysis, if the heating is not prolonged for more than

ISSN:0028-0836    

DOI:10.1038/119425b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE letter by Mr. Hanawalt and Prof. Ingersoll on “Non-Magnetic Films of Iron, Nickel, and Cobalt “ (NATURE, Feb. 12, p. 234) raises a number of interestin questions.Oseen's explanation (Z. fur Phys., 32, 940; 1925) of the properties of the previously announced nonmagnetic films of nickel was based on the supposition that 'non-magnetic' signified not only the loss of ferromagnetism but also of the magnetic moment of the nickel atom itself. An electronic rearrangement but no other change was postulated as a result of which the nickel atom obtained a completely symmetrical configuration, thus leading to a non-magnetic film in the above double sense. It may be pointed out that, while such an explanation could be extended to the case of iron, it would not be applicable for cobalt, as this atom contains an odd number of electrons It is not possible to state definitely from the data so far published whether the term 'non-magnetic' should be interpreted as in Oseen's paper or merely as indicating a loss of ferromagnetism as it is apparently intended. So far as the physical nature of the non-magnetic films is concerned, it seems that these may differ from the ordinary metals in bulk in that (1) the metallic atoms are farther apart; (2) chemical combination probably of a rather loose type may have taken place; and (3) there may have been an electronic rearrangement in the metallic atoms. (1) is shown to be the case from Hanawalt and Ingersoll's observations, and (2) is rendered probable. The reality of either (2) or (3) or both could be determined if it were possible to state whether the material of these non-magnetic films is diamagnetic or paramagnetic, and in the latter case, by measuring the susceptibility over a range of temperature, to evaluate the magnetic moment of the metallic atoms. The occurrence of paramagnetism would be consistent with the existence of change (1) with or without (2) and (3). A knowledge of the actual magnetic moment would probably enable a definite decision to be made as to the reality of changes (2) and (3).If diamagnetism were found and the films of iron, cobalt, and nickel are really of a similar nature, then it would be very probable that all three changes had taken place. The metallic ions would then be in states which might correspond to that of iron in, say, K4Fe(CN)6, cobalt in most co-ordination compounds of tervalent cobalt, and nickel in, say, Na2Ni(C

ISSN:0028-0836    

DOI:10.1038/119426b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE following conclusions, amongst others, have been reached during an investigation on the effect of ‘antiknocks’—such as lead tetraethyl—on ‘ knocking ’ in petrol engines:(1) Antiknocks do not influence detonation in rapid combustion mixtures (Proc. Roy. Soc., II 4, 137, 1927). (2) They function in the initial stages of the combustion as negative catalysts. In the slow combustion of a hydrocarbon, aldehydes are produced which readily form peroxides, which auto-catalyse or induce oxidation of the earlier stages. If these are removed, combustion proceeds more slowly. By reason of such effects on the processes of slow combustion preceding ignition, ' antiknocks' influence greatly the igniting temperature, particularly in the case of aldehydes. Similarly they effect those same processes which occur at a flame front in a comparatively slow burning mixture.(3) Those metals which give effective organometallic antiknocks are found to be capable of forming higher oxides. Such metals as potassium, which form peroxides in equilibrium with other oxides at about 4000 C. are very effective. Non-oxidisable metals such as gold are ineffective. The unstable peroxide formed in the combustion of the fuel and the metallic peroxide are considered mutually to destroy each other. The rate of destruction of the positive catalyst is greater than its rate of production, so that combustion is delayed. The metal atoms in a state of incipient oxidation are thus the effective anticatalysts. (4) A purely organic antiknock like aniline is effective for the same reasons; only those types of organic substances are effective as antiknocks as have been shown to be effective in retarding the oxidation of certain aldehydes at normal temperatures in the liquid phase. The mechanism adduced to explain their action in such circumstances by Moureu and Dufraisse is similar to that which we have given above. Such organic antiknocks themselves undergo combustion and are destroyed, a larger quantity of the negative catalyst being therefore required for the same effect..(5) Both for 'ignition' and 'knocking' there is a condition of sensitiveness to change of reaction rate, and the effect of 'antiknocks' is in general much the same on the two phenomena. The views given are supported by the effect of such substances (aldehydes, organic peroxides, etc.) which promote knocking or favour ignitibility. These conclusions elaborated and the experimental data which suggest them, will be detailed in papers which it is hoped soon

ISSN:0028-0836    

DOI:10.1038/119427a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE immense present-day importance of radio communication has directed the attention of a wider circle than ever before to the conditions prevailing at great heights in the atmosphere. Even to the professional meteorologist it seemed formerly that what happens above a height of 30 or 40 kilometres has no bearing on the practical affairs of humanity, however interesting the problems of these upper levels might be to the pure theorist. Almost the only influence of these levels upon the technical operations of mankind seemed to consist in the occasional interruption of telegraphic communication at times of great magnetic storms and aurora] displays; the interference was pretty clearly due to currents induced in the earth and the cables by the rapidly varying magnetic field, but the direct association of the latter with the upper atmosphere was somewhat hypothetical, though the auror e were quite indubitably atmospheric phenomena.Now that signal transmission is not confined to cables, and electromagnetic oscillations over a wide range of wave-length are sent out into space, the upper air assumes more direct importance, for it is known that a large part of the energy transmitted to distant points travels intermediately at high levels. The manner in which the waves are affected in the upper levels is already partly understood; the rate of propagation is increased by the presence of ions, so that if the ionisation increases with height the upper part of a wave front travelling at an upward inclination to the horizontal is tilted forward, and the wave train may thus be refracted downwards again, quite sharp angles of bending being possible. At the same time, some of the energy of the wave, communicated to the ions, is lost by the latter during collisions with surrounding molecules; if the mean free path of the ions is short, and collisions frequent, the energy of the waves may be rapidly absorbed; the absorption increases with the density of the ionised layer, and is greater for long (low frequency) waves than for short waves. Moreover, the earth's magnetic field deflects the ions while they are oscillating under the influence of the waves, and brings about a change of polarisation of the waves, which is responsible for some of the errors in direction-finding by wireless. These facts make it clear that changes in the ionisation of the upper atmosphere have an important bearing on wireless transmission, and should be carefully investigated in order that, if possible, the methods of signalling may be adjusted to the changing conditions. Probably in the future the upper atmospheric phenomena will become known by wireless investigations themselves with a thoroughness and detail not otherwise attainable -the results already achieved seem to promise this. But, at least in these early days of such work, some help towards the understanding of wireless problems may be gained from the knowledge slowly accumulated during three or four generations by the study of solar phenomena, aurorae, and terrestrial magnetism.The ionisation of the atmosphere at high levels may be partly due to the penetrating radiation studied by Kolh6rster, Hess, and Millikan, or by the runaway electrons the probable occurrence of which during thunderstorms has been pointed out by C. T. R. Wilson. It seems unlikely, however, that the ionisation thus produced is comparable in importance with that due to solar action. The magnetic variations are intimately connected with the ionisation of the upper atmosphere, and indicate its general distribution and its more important changes, which are unmistakably associated with the state of the sun, or its presentation towards the earth. Further study may reveal magnetic phenomena indicative of ionisation unconnected with the sun, but it appears improbable that such can be of the same order of magnitude as that of which the sun is obviously the cause. The sun ionises the upper air by two independent agents. One of these travels rectilinearly and falls only on the hemisphere of the earth which faces the sun, that is, on the day or sunlit hemisphere. Many facts indicate that this agent is ultra-violet radiation, absorbed in the upper atmosphere, principally by ozone, itself produced by the first stage of such absorption; another consequence is that the temperature of the layer in question (extending upwards from about 50 km. height) is raised above that of the air at ground-level. As the revolving earth carries any particular region of the atmosphere into the night, when the ionising radiation is cut off, the ions re-combine, and most rapidly at the lower surface, which in the course of a few hours moves upward from a level of about 50 km. to 100 km. or more. The conductivity of the ionised layer is consequently diminished at night, by the reduction in both the thickness and the specific conductivity; this affects the electric currents flowing in the ionised layer, to which the daily magnetic variations are due. The latter are much more intense by day than by night, and in low latitudes (where the sun's rays are most direct) than in regions farther from the equator. The magnetic variations also show clearly that the conductivity of the layer ionised in this way is distinctly greater (by at least 25 per cent.) at sunspot maximum than at sunspot minimum; this requires a change of intensity in the ultraviolet radiation by about 60 per cent., which is remarkable in view of the absence of any comparable variation, during the sunspot cycle, in the sun's visible radiation. The increase in the ultraviolet radiation seems to be due to enhanced emission from the sun's surface as a whole, and to be independent of particular disturbed localities on the sun.The other solar ionising agent is corpuscular, and proceeds from locally disturbed areas on the sun's surface, often, though not always, associated with visible markings such as sunspots. The corpuscles are ejected in laterally limited streams, the direction of which varies as the sun rotates. When such a stream happens to impinge on the earth, the air becomes highly ionised in the atmospheric regions affected, which are situated geographically within about 200 of the poles of the axis of magnetisation of the earth, though they spread farther towards the equator when the streams are specially intense. The corpuscles can penetrate the earth's atmosphere down to not less than 80 km. above the ground; they impinge not only on the side of the earth facing the sun, but also bend round to the right side of the earth, where they produce visible aurorae. The deflexion of the corpuscles towards the magnetic poles is due to the earth's magnetic field, and indicates that the streams have a slight excess charge and are ionised. The ionisation of the auroral zones renders these regions of the atmosphere highly conducting, and permits intense electric currents to flow in them; the changing magnetic field of these currents is observed as a magnetic storm (or lesser disturbance). Even if auroroB were not visible, the magnetic observations would indicate the existence of highly conducting upper air in polar regions.The ionisation of the air due to the solar corpuscles is much less uniformly distributed than the ionisation over the sunlit hemisphere due to ultra-violet radiation; the limited distribution of bright aurorae gives visible indication of this. Also the ionisation by corpuscles varies irregularly with time, and cannot be predicted at present with any certainty; it depends both on the activity and presentation (towards the earth) of the disturbed solar areas. If such an area remains active after the lapse of a solar rotation period (about 27 days), it may affect the earth a second time, or even several times after successive rotations. Hence arises the clearly marked tendency for magnetic disturbance to recur after 27 days; but this is only a tendency, for the direction of the stream from a solar disturbed area may change, or the area may not remain long active.The influence upon wireless transmission of the regular change of ionisation from day to night has long been recognised; the improved conditions at night, especially for long waves, are naturally accounted for by the withdrawal of the refracting ionised layer to greater heights at night, where the ions have longer free paths and where their less frequent collisions dissipate less of the energy acquired from the electric waves. The influence upon wireless of the less regularly distributed but occasionally very intense ionisation due to solar corpuscles has only lately become reasonably certain. The effects are likely to be complicated, and it will doubtless be a long time before they are clearly ascertained. An interesting feature suggested by recent observations is that transmission from Europe to America is more affected than that from Europe to the East. This is not unexpected, in view of the inclination of the earth's magnetic to its geographical axis; the centre of the north auroral zone is about 100 from the geographical north pole, in the direction of Canada, and aurorae are observed in Canada in much lower latitudes than in Europe. The region of abnormal corpuscular ionisation will therefore extend about 200 farther towards the equator in Canada than in Russia.

ISSN:0028-0836    

DOI:10.1038/119428a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature