摘要:

IT is distinctly unfortunate that the first seven plenary sessions of the imperial Agricultural Research Confere held during the week in which two p a arjies,l7/ keii) annual conferences. The subject matter fiscussion at the research confeence is of te greatest significance to an Empire in]l541e foremost industry is agriculture and /he future of which depends wholly upon the progressive realisation of the vast potential resources of the lands which it embraces. Nothing has been left undone by the Empire Marketing Board and the Ministry of Agriculture to emphasise these two points. The reports, memoranda, and pamphlets which they have prepared and distributed to the delegates present for their information and guidance in discussing the various items on the agenda are calculated to interest a wide public, and would undoubtedly have been extensively used by the Press for this purpose had the meetings to which they refer been held a week earlier. It can scarcely be expected, however, that the Press will give undue prominence to a conference dealing with such impersonal and serious questions as those relating to the influence of scientific research upon our economic position, unless they are dealt with in a brilliantly illuminating and arresting manner and by speakers who have attained a position in popular esteem which rivals that held by the leaders of the Conservative Party and the Labour Party respectively.The items on the agenda were so arranged that the plenary sessions during the opening week were devoted to the consideration of administrative questions. The task of considering the agricultural problems confronting the various parts of the Empire, for the solution of which the aid of science must be invoked, has been delegated to groups of specialists. Now it cannot be suggested seriously that any of the so-called technical questions which have been delegated for the consideration and report of specialist commissions, questions affecting veterinary science, soils and fertilisers, plant pathology, the preservation and transport of food and raw materials, animal and plant genetics, agricultural economics and dairying, are without interest for any of the delegates present at the Conference. Time spent on the discussion of the problems related to these various branches of agricultural research would have been exceedingly well spent. The delegates would have been able to grasp the magnitude of the, responsibilities of the agricultural services, they would have been able to envisage their problems as a whole and the inter-relations of the work already being carritd out in various constituent parts of the Empire, and to survey the possibilities of co-operation in connexion with the researches already in progress arid those others which the Conference might decide were imperatively needed. However, it was pre-ordained that the Conference shouldgive first consideration to administrative questions relating to staffs and institutions. The discussions which arose out of them at the plenary sessions are certainly illuminating. In connexion with man-power, it was alleged that there is a serious shortage of suitable candidates for most branches of scientific services supported by Governments, a shortage which is being accentuated by the growing demand for specialist officers made by the non-self-governing dependencies. The Research Sub-Committee of the Imperial Conference attributed this shortage to the wholly inadequate appreciation of the importance and value of scientific research on the part of the public, of the Press, and even of Governments themselves: to the uncertainty in the minds of students embarking on a university course as to the career offered by agricultural research: to the increasing demand by private employers for men with a university training in science: and to the lack of knowledge shown by educational institutions and parents of the careers available overseas in the various branches of science and their special attractions. The shortage of candidates is particularly acute in the services—other than medical for which a training in the biological sciences is a requirement.The only satisfactory and permanent remedy for this state of affairs, suggested Lord Lovat, Parliamentary Secretary of State for the Dominions, is to make the Agricultural Research Services in pay, status, career, and rewards the equal of other Government services carrying equal duties and responsibilities. Tt is folly to expect that the best men from the universities will be attracted to agricultural science while there are so few definite and certain prizes at the top. High initial pay is an insufficient inducement. Practically every subsequent speaker endorsed these views, which will obviously commend themselves to every scientific worker in the Empire. These are the views which have been advanced from time to time in our columns. Generally speaking, the flow of entrants to a career is regulated by its attractiveness, and not the least attractive aspect of a career is its estimation in the public esteem. This esteem must be more than a recognition of the money value of those officers who enter specialist services; it should include a proper understanding of their creative outlook. Nothing has done more harm to scientific workers than the popular acceptance of the theory that those who have achieved eminence in a particular field of science have become so specialised in their interests and so biased as to render them unfit for positions of administrative responsibility. Too ealy specialisation in a student's career would, it is true, tend to produce an undesirable narrowing of outlook, but provided specialisation is left to the post-graduate stage of a student's educational career, there could be no better preliminary training for future administrators than that provided by a liberal and general course in science. This fact has been recognised by certain provincial governments in India. They have been recruiting their Indian administrative staffs from the scientific institutions, particularly the colleges of agriculture in their provinces, and have found this method thoroughly satisfactory.It is imperative that any general science course in the schools should include general biology as a subject and should not be confined, as it is in most schools in Great Britain, to physical and chemical science. The interest which is stimulated in a subject at school has a direct bearing upon the course of study undertaken at a university. Moreover, as Sir Daniel Hall rightly observed, biology should be taught in the schools not only because the Empire will have to make greater and greater demands for trained investigators in the field of biology, but also because no man can properly be regarded as well-educated who does not fundamentally understand how a plant grows and how an animal lives and has its being. If, moreover, as Sir John Farmer pointed out, an interest in biology were stimulated in the schools, it would not be taken up as a soft-option' at the universities mainly by those students who were conscious of their deficiencies in physics and chemistry. The suggestion that the shortage of biological students at the universities is due to the lack of endowments for biological study was discounted by Major Walter Elliott. He emphasised the fact that there is no shortage of candidates for the medical schools, for the obvious reason that parents are satisfied that medicine provides a satisfactory career for their sons and daughters. To the proposition that scholarships should be provided for public and other secondary schoolboys to enable them to take up agricultural science at the university under the condition that they afterwards entered the agricultural service, he was resolutely opposed. This inducement, like the provision of pensions under the Civil Service scheme for the retention of officers in the service, he regarded as coming within Sir James Currie's definition of "ttracting candidates by means of well-baited but otherwise poor booby-traps." Various other means of stimulating recruitment to the overseas services were discussed. It was pointed out that varus post-graduate scholarship schemes in existence have been successful in this regard. Those scholarships provided by the Government, tenable at the Imperial College of Agriculture at Trinidad, have already provided a number of officers for the colonial agricultural services in the Tropics. The scheme of the Empire Cotton Corporation has also been successful in obtaining men for cotton research in various territories. On the other hand, no success has so far attended the efforts of the Australian Commonwealth Government to obtain recruits for certain biological services by the grant of similar scholarships. The Commonwealth offered post-graduate scholarships to the value of £300 a year for two years, with £150 travelling allowance, in addition to the payment of all special fees in connexion with study. Some of these scholarships were offered to enable students to specialise in mycology and genetics. On the completion of their course, they were to be guaranteed at least three years employment under government at a minimum salary of £400 for the first year, £450 for the second, and £500 for the third. No applications were received for these scholarships. This was attributed to the past neglect of the agricultural services by the Australian Government and the failure of the people of Australia to appreciate the need for agricultural research.Generally speaking, the discussion on training and recruitment was disappointing. It is true that much that needs saying has been said several times already in the past twelve months at gatherings of Imperial delegates, so that it was difficult to escape the platitudinous. But since every representative of the Home Government present subscribed to the view that the Imperial Agricultural Research Service must provide an attractive career for first-class men, if it is adequately to fulfil its prescribed functions, it is reasonable to expect that they should have defined its attractiveness in specific terms, and stated what further financial provision the Government is prepared to make, and what financial support has been promised or is expected from the IJominions and non-self-governing Dependencies, for the effective carrying out of the schemes submitted to the delegates for their consideration. It is to be hoped that some definite statement of this character will be made before the break-up of the Confer

ISSN:0028-0836    

DOI:10.1038/120537a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE Vice-Chancellor, in his recent address at the commercement of the academic year at Cambridge, referrd to the heavy strain which has fallen during the past year upon the administrative officers of the(university-the Registrary, the Secretary of the i'Ieral Board, the Treasurer, and, we may add, the Vice-Chancellor himself and upon the members of various boards and committees. When 1000 pages of ordinances have to be recast to meet the requirements of new statutes, the labour involved must necessarily be extremely heavy. It may not be without interest to inquire after a year's working how far the results obtained justify not only last year's work, but also the heavy work involved over a period of years by the labours of the Royal Commission and the subsequent Statutory Conimission. What are the gains of the new scheme? The first one that strikes the eye at once is the feeling of security that the younger married don' has gained through the existence of a pension scheme of the same type as holds in the other universities of Great Britain. This means a comparative freedom from serious financial anxiety, and it makes easier the free interchange of teachers between Cambridge and other universities. Coupled with this is the advantage to the University which must accrue from a scheme which ensures the retirement of the teaching staff on reaching an age limit. Opinion will vary as to the proper age for retirement and the benefit that comes from a rigorous compulsory scheme, but it is clear that the scheme is, on the whole, a definite improvement on the old order of things.Financially, many teachers in the University also benefit by the increased stipends which the annual grant to the University secured by the Commission has made possible. University stipends still lag behind the corresponding figures for professional careers outside, but the disgrace of the charity pittance awarded in the past to distinguished teachers has been stopped. ft is for the University to watch that fresh developments are not marred by inadequate financial arrangements. This may check some of the valuable growths which in the past have come from poor beginnings; an enlightened policy should see to it that such growth should be encouraged, but with a start oii a bettcr basis, The real gain of the Commission is that the University has now secured control of the development of its educational policy to an extent that was impossible before. The General Board of the Faculties, with its control over the finances of the purely teaching side of the University, has become the most important body in the University. The faculties, acting through their appointment committees, have control of the appointment of new teachers and are not so dependent as before on the chance appointment by the colleges of members of college staffs. It is significant of the change how many of the vacancies of the past year in lecture- ships have been filled by candidates from outside Cambridge. This widening of the field must be a pure gain to the University.This would not be the case if the chances of promotion of the best sons of Cambridge to office in the University were blocked by the new scheme. It may be that the process of co-operation between faculties and colleges in making their staff appointments has not yet been fully explored. The ideal scheme by which the University and the college should each take its share in supporting the man who divides his time between the two of them may take some time to hammer out, but the new statutes make such a scheme possible and practicable. Goodwill and organisation will do the rest. Among other gains requiring mention are the opening of most University prizes, scholarships, studentships, and teaching posts to women, the improved financial position of the University Library, the casing of University taxation on the smaller colleges—here it must be admitted at the expense of the larger and richer foundations—and the official recognition of research as part of the University's duty.There are necessarily difficulties, and here and there doubts and regrets. Tt is incumbent on those responsible not to let organisation become dominant and not to press the professors with too much departmental administrative work. The Vice- Chancellor, we believe rightly, attributed the comparative lack of discussion of recent changes in the ordinances to " disposition to settle down to work arid to put the new Statutes of the University and the Colleges to the test of practice." The University may well spend a year or two in rounding off the fruitful work of the Commission and making quietly the further changes which experience shows to be desirable and necess

ISSN:0028-0836    

DOI:10.1038/120539a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

CATALYSIS is a subject which has always J excited the interest of chemists—sometimes,indeed, their prejudices and passions. There is one point, however, on which they are probably all agreed, namely, that the association between the catalyst and the substances the reactions of which it catalyses is of so specific a nature that it is proper to apply the term chemical,' On the other hand, to understand the mechanism of the large class of chemical reactions which take place in contact with solid catalysts, it is necessary to inquire into the physical nature of the interfacial region where the surface catalysis takes place, and this introduces all the phenomena of adsorption.' For some purposes it is more important to know about the adsorption equilibria than about the nature of the forces which hold the adsorbed molecules to the surface; and there has occasionally arisen a quite unnecessary distinction between chemical' and physical' theories of catalysis. In recent years, however, Langmuir has done much to dispel the idea of any such antithesis. The truth about catalysis has many aspects, one or other of which becomes of predominating importance according to the problem under consideration. There are two great objects: one is to arrive at an understanding of the nature of chemical change in general, and the other is to be able to control specific reactions for particular ends, possibly industrial. The two books under review are quite different in scope and method. That of Rideal and Taylor is of a quite general character, and deals with both the chemical and physical aspects of catalysis and with its industrial applications; that of Sabatier is written entirely from the specific chemical point of view.(1) "La Catalyse en chimie organique" is already well known to most chemists either in the French edition or in the English translation by Prof. Reid. It is an inexhaustible source of information about the multitudinous organic reactions which can be catalytically controlled. These reactions must be regarded as forming almost a separate branch of chemistry, and one which is becoming yearly more important. It is only necessary to think of the convenient catalytic process for the dehydration of alcohol to ethylene, compared with the traditional procedure, to understand what industry owes to catalytic chemistry. It is often possible to make at least a shrewd guess at the kind of catalyst which will be most effective in provoking some desired reaction. Although most of the information about catalytic organic chemistry is purely empirical, nevertheless the vague outlines of general laws are in places dimly discernible. Definite rules, which would enable catalytic influences to be predicted a priori, cannot of course be formulated, but Sabatier succeeds in bringing many hundreds of reactions into a degree of co-ordination which is surprising. The picture he presents is not more chaotic than that, say, of inorganic chemistry fifty years ago. The analysis and arrangement of the material is masterly, and admiration is increased by the reflection that a very large portion is derived from Sabatier's own researches.It is interesting to read the statement that Sabatier's own work on catalysis has been guided by the hypothesis that unstable intermediate compounds between the reacting substances and the catalyst are always formed. In the introductory part of the book, which occupies about fifty pages, he develops a general theory based upon this idea, and shows convincingly the fundamental part played by specific chemical interaction. This aspect is a very important one, indeed all-important, since Sabatier is concerned solely with the nature of reaction products, and not at all with the kinetic problems connected with the mechanism of reactions, or with the relation between reaction rate and concentration. To deal with these, however, it would have been necessary to take into account the physical chemistry of the processes in a manner similar to that of Langmuir and others. For the purposes of his treatment, then, Sabatier has quite rightly laid all the stress on the specific chemical influences; but it must be remarked that for the physical chemist in search of examples on which to test his theories, this book provides the best storehouse of raw material that could be imagined.After three introductory chapters of a general nature, there follows a classified survey of different types of reaction, beginning with isomerisations, polymerisations, and condensations. The following chapters deal in order with reductions, hydrations, hydrogenations, various decompositions, dehydrogenations, dehydrations, the decompositions of acids and esters, the splitting off of halogen hydrides, the decomposition of hydrocarbons, and the hydrogenation of fats. The translation of the French text appears to be accurate, if here and there very slightly on the side of freedom, and the German edition possesses an index, the absence of which was an almost intolerable disadvantage of the original. This disadvantage is specially felt in what is in some respects a work of reference. The translation contains 83 pages of additions, covering the years 1920—1924, and a synopsis, not very complete, of papers which have appeared since 1q24. In the theoretical part of this appendix are two scanty references to Longmuir.'(2) Since the original edition of "Catalysis in Theory and Practice" was published, considerable advances in the theoretical aspects of the subject have been made, and industrial applications have developed and multiplied. The theoretical parts have been completely re-written for the new edition, and much additional matter relating to modern developments on the practical side has been put in. Two introductory chapters deal with the early history of catalysis, and criteria of catalysis.' Then general theories about the nature of chemical change are discussed under the headings Homogeneous Reactions,' and The Theory of Heterogeneous Catalytic Reactions,' homogeneous reactions providing a standard with which catalytic reactions may be compared and contrasted. The subjects of promoter action and catalyst poisons are then dealt with, after which various chapters deal with the applications of catalysts to processes of oxidation, hydrogenation, and so on.To the reviewer the most interesting parts of the book are, perhaps, those c[ealing with technical processes. There is, for example, an excellent discussion of the general problem of the reduction of the oxides of carbon, with an account of the modern methods of producing methyl alcohol from water gas. In this, and other similar examples, the authors have shown the application of the theoretical principles to practical problems in an illuminating way. Information is to be found in different parts of the book on such varied matters as the cracking of oils, the production of synthetic rubber, the hydrogenation of fats, and the production of aniline black. It is always a difficult problem, in a book which aims at completeness, to decide how far the author should merely quote the work and views of others, and how far he should criticise and re-interpret. On the whole, Rideal and Taylor have compromised well between the possible extremes.No book dealing with a rapidly developing subject could be written every page of which would compel unqualified assent. On p. 82, for example, it is stated that to account for proportionality of reaction rate to a fractional power of the pressure in a heterogeneous reaction, it is necessary to assume that each molecule of one of the reacting gases occupies some definite integral number of elementary spaces on the lattice of the solid. There is a much simpler explanation. When the degree of adsorption of a gas like stibine is large, the rate of its chemical change is independent of the pressure; when the adsorption is small, the rate is directly proportional to the first power of the presswre. For intermediate degrees of adsorption, therefore, the rate of reaction must vary as some fractional power, which, in point of fact, is never quite constant. The production of the book is very good indeed. It irhaps a pity that more care was not taken over proper names; it was, for example, Knietsch,' and not ˜Kneitsch,' who did pioneer work on the contact process, and McC. Lewis' is rather colloquial. These minor blemishes should be removed when possible from a book which will be of importance to all chemists for some time to come

ISSN:0028-0836    

DOI:10.1038/120540a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE "Lezioni di calcolo differenziale assoluto" by Prof. Levi-Civitø  were published in Italian in 1925. This account of the foundations of the absolute differential calculus has now been translated into English. Miss Long has thus conferred a benefit upon British mathematicians for which they will be very grateful. The subject is of fundamental importance in the applications of mathematical methods to modern theoretical physics; the treatment is as masterly as can be expected, coming as it does from the lecture notes of one of the outNo. standing exponents of the subject and one of the outstanding contributors to its development; the translation is excellent, combining, as Prof. Levi- Civitø  says in the preface, " scrupulous respect for the text with its effective adaptation to the spirit of the English language." It is more than a mere translation, however, that we have before us now. More than 150 pages are devoted to two new chapters, written specially by Prof. Levi-Civitø , dealing with the fundamental principles of Einsteins general theory of relativity, including as a limiting case the special theory, as an application of the absolute calculus. More than one-third of the book is therefore new, and it is a privilege to British mathematicians to have this addition to the original contents published in the English language. This treatment of the theory of relativity possesses distinctive features, which give it added value. The present writer has for a long time thought that the study of relativistic mechanics should be presented on the basis of the classical Newtonian mechanics. This would have obvious advantages, the most important being that the essentials in the transition from the conceptions in the classical dynamics to the conceptions in the relativistic dynamics could be presented clearly and effectively, instead of being lost in a maze of optics and electromagnetics. Further, it is surely reasonable to claim that the study of the space- time manifold is fundamentally a kinematic exercise, although the causes which have led to the modern view of space-time are derived from astronomical, optical, and electromagnetic experiences.Prof. Levi-Civitø  has adopted this viewpoint He traces the relativistic evolution of mechanics, including geometrical optics, which in the theory of relativity is based upon the conception of a light ray as a special case of the path of a massless particle. He also adds another distinctive characteristic in the fact that he does not lay down the postulates of relativistic mechanics in abstract form, as so many new laws introduced arbitrarily, but proceeds inductively from the classical mechanics to discover modifications which are forced upon us if we take account of the principle of relativity. Starting off with Hamilton's principle for the motion of a free particle, Prof. Levi-Civitø  first shows that it is possible to apply the same treatment to the time, co-ordinate as to the three space co-ordinates of the particle, with reference to the variational equation 8 J Ldt 0. Introducing the form L/c2 = 1 1 T, which for a very large value of c is approximatelythe same as L =v2 + U, the classical form of the Lagranian function, the equation 8fds = 0 is obtained, where ds2 can be expressed in terms of any four co-ordinates as a general quad ratic form.The results of the special theory of relativity follow at once by putting U zero, and the author deduces the Lorentz transformation and all its familiar consequences. Further, the extension to space- time manifolds differing from the pseudo-Euclidean space-time in the special theory is a comparatively simple conception, the world lines of a free particle being the geodesics in its space-time continuum. Particular attention is devoted to geodesics of zero length, or light rays, where s cannot be used as the independent variable. The equations of motion of a continuous system are obtained in the same inductive manner and the introduction of th e energy tensor justified.Having defined the Einstein tensor and the gravitational tensor in the older form, with divergence zero, Prof. Levi-Civitø  writes down Einstein's equations of the gravitational field (without the cosmological term). He at once proceeds to deal with the statical problem, thus separating the time- like from the space-like terms, and shows how to a first approximation the Newtonian field is obtained. After the crucial phenomena' the author attacks the problem of fields having spherical symmetry, dealing with the Schwarzsehild, the Einstein, and the de Sitter solutions, and introducing the cosmological term. No reference is made to Einstein's new form of the equations of the gravitational field, which does not affect the field in empty space, but introduces modifications into the field inside matter. Of the large number of books that have appeared in the English language on the theory of relativity, very few have had anything very original to contribute. Prof. Levi-Civitø 's book in its English translation is a notable addition to the literature

ISSN:0028-0836    

DOI:10.1038/120542a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

BOTH these books are by Viennese biologists, who describe their observations during tours of one to Japan and of the other to America. Prof. Molisek was from 1922 until 1925 on the staff of the Botanical Section of the Biological Institute of the Sendai University in Japan. He has already, in his " Pflanzenbiologie in Japan," recorded his special observations, and in this book writes of his journeys to and fro and in Japan, as he puts it, as a " globe trotter." He is, however, a highly trained, skilled observer, and he writes an interesting account of his voyages out and home, and of the various phases of Japanese life. He describes, amongst other topics, life and sports at the Japanese universities and schools, the theatre, the magic mirror, fishing by cormorant, the hot springs, the ascent of Fujiyama, the aboriginal race—the hairy Ainu, the earthquake of 1923, and Japanese horticulture, fruits, and vegetables. Prof. 0. Abel's account of his visit to the United States and some of the West Indian islands in 1925, at the invitation of the International Education Board, contains more original matter. is professor of pakeobiology and visited many localities famous for their evidence on geological ecology, and he expresses on their problems a competent, independent judgment. He visited the American museums rich in fossil vertebrates, he examined the quarries in Connecticut famous for their Triassie footprints; his visit to the mangrove belts in Florida and the West Indies leads to the conclusion that the Flysch of the Alpine belt, which has been regarded as the deposit of mud volcanoes or of deep seas, is the mud of ancient mangrove swamps, deposited when Central Europe consisted of a group of islands and had a tropical climate; in Florida he examined the beds at Vero which have yielded remains of fossil man, and concludes that the man was not as old as the associated fossils; he discusses the West Indian fauna and explains the various continental visitors to the islands not by land bridges but by mangrove bridges, and his interesting chapter on this problem illustrates the extent to which biologists, whose conclusions depend so largely on negative evidence, overlook the direct tectonic evidence. In Western America, Prof. Abel visited the Grand Canyon and the Brea deposit at Los Angeles which has yielded such a rich Pleistocene mammal fauna, and also the fossil quarries of Nebraska; there he also examined Themonelix, an obscure fossil which has been regarded either as due to a burrowing animal or to plant roots; and he advocates the latter.Both books are richly illustrated by excellent photographs, and many of these by Prof. Abel are of the specimens he collected. He gives many references to the literature, so that the book is a useful guide to recent contributions to rnauy problems in American geology. In his account of the bone beds of Nebraska he explains their origin by the crowding of the animals on to hill-tops at times of flood; and in reference to the opposite explanation, that they were bogged beside drying pools in time of drought, he quotes a sentence which he attributes to W. K. Gregory instead of to the present write

ISSN:0028-0836    

DOI:10.1038/120543a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

Tins autobiography of one of the Winnebago Indians living on the Nebraska side of the Missouri River, is a remarkable document. It may he regarded either as a piece of anthropological evidence or as material for psychological study. Its engaging frankness and entire absence of a moral viewpoint are illuminating. At the same time it must be admitted that from neither point of view do the conditions which this record reveals seem such as are conducive to the welfare and preservation of the Indian, if they can be regarded as typical. It is perhaps significant that in seventeen years a Presbyterian mission had in 1909 converted one family only. This suggests a conservatism which adds to the value of the autobiography as a record of tribal custom and tradition. Anthropologists who have worked in the field are well aware of the difficulty of getting at the subjective side of the information they seek. In this document custom, ritual, and belief take their proper place as integral elements in proper perspective in the everyday life of the individual.

ISSN:0028-0836    

DOI:10.1038/120544c0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

SOME years ago, Prof. Joly (Proc. Roy. Soc., A,102, 682; 1923) discovered radioactive haloes which could not be ascribed to any known radioactive product. One class, not unlike thorium haloes, he calledX-haloes; asecond class, of radii less than those of other haloes, he called ‘hibernium’ haloes, hibernium being the suggested name for the new radioelement causing the halo. Recently, S. Iimori and J. Yoshimura(Sci. Papers Inst. Phys. Ghem. Res. Tokyo,5,11; 1926) have found a class of haloes not unlikeX-haloes which they callZ-haloes. They suggest that theX-haloes and possibly the haloes ascribed by Prof. Joly to radon are identical with these, and that they are due to products of the actinium series.Z-Haloes have some times two inner rings smaller in radius than any caused by a known radioactive product, and these they ascribe to two uranium isotopes at the head of the actinium series with half-value periods of the orders of 1012and 1023years. They also state that their work onZ-haloes definitely establishes that the actinium series originates independently of the uranium series.The Japanese workers are, I think, probably right in their ascription of the Z-haloes to actinium products, but in identifying radon haloes with actinium haloes, and in ascribing the two very small rings to isotopes of uranium, they have missed an important point. The actinium series cannot be regarded as originating independently of the uranium series in view of the strong experimental evidence to the contrary. Moreover, if the actinium series has uranium isotopes, as they suggest it has, how did these get separated from uranium itself to form a halo unmasked by that due to uranium and its products ? They have evidently not considered this. The only answer I can suggest is that the uranium isotopes which originate the actinium series giving the Z-haloes are end-products of elements of atomic number greater than 92 and so have not necessarily mixed with ordinary uranium. I think the explanation of the unexplained rings and haloes is probably simple and involves two things: isolation of radioactive products from known minerals by chemical agencies, and the possession of feeble radioactivity by some of the so-called end- products.It is known(W. Marckwald and Russell) that uranium minerals may be so altered by agencies like percolating water that, while the presence of the equilibrium amount of ionium testifies to their great age, they are anomalous in possessing no lead, a fraction only of their equilibrium amount of radium and, as unpublished work of mine shows, a fraction only of their protoactinium. Let us consider what is likely to occur each of the different elements present in a primary uranium mineral were isolated by chemical agencies and ,afterwards formed a halo in the mica with the particles they emit. Isolation of element 91 would isolate protoactinium and lead to the formation of the halo characteristic of the actinium series; isolation of elements 90 and 88 would lead to uranium haloes in different stages of development; isolation of element 89 would lead to actinium haloes minus the ring due to protoactinium; isolation of element 86 would lead to the characteristic radon halo discovered by Prof. Joly; isolation of elements 84 and 83 would lead to a single ring characteristic of polonium; isolation of element 82 would perhaps lead to the polonium ring and to any rings due to possible a-particle activities from the end-products; no halo is,..to be expected from the isolation of the quick- changing products of element 8 1 . Thorium minerals may be similarly considered. Now it is not unlikely that some of the end-products of atomic number 82 may he found to be feebly radioactive. For theoretical reasons too lengthy to be given here I find that possible end-products of atomic nasses 204, 205, 206, and 207 are unlikely to possess any radioactivity, while those of masses 210, 209, and 2;c18 may be feebly radioactive, and that, of these three, aitinium-, of mass 209 (NATURE, Sept. 17, p. 402), is likely to be more unstable than the two others. Now, for a given half-value period, an ct-rayer of the actinium series has a larger range than an a-rayer of the thorium or uranium series. The a-particle from the product of mass 209 might therefore be expected to have a longer range than those from the two other products, but shorter than the a - particles from uranium or thorium.The identification by S. Iimori and J. Yoshimura of Z-haloes with X-haloes was made, not by a comparison with their own of Prof. Joly's published measurements, but from observations of his photo- graphs. (The published measurements of both sets of haloes do not, in fact, agree well.) For a reason I know not, the radii of the rings of uranium and thorium haloes measured by the Japanese agree closely with those to be expected theoretically, while those of Prof. Joly are generally smaller, the deviation from theory being the greater the shorter the range of the ct-particle. A straight -line relation appears to connect the theoretical with his observed radii of the rings, and, using it, I have calculated the radii of the rings of Prof. Joly's unexplained haloes to compare them with the other measurements. The smallest ring observed has then a radius of 7, 54, and 63 in hibernium-, Z1-, and Z2-haloes respectively, and the second smallest ring has a radius of 1 1 0, 105, 108, and 107 in two different sets of X-haloes, in a Z1-halo and in an unnamed halo respectively. Each of these rings is too small in radius to be ascribed to any active radioelement. The larger of these I ascribe to actinium-1 (mass 209), and the smaller to both radium-12' (mass 210) and to thorium-1 (mass 208). On this view, if lead alone were isolated from auranium mineral, a single ring, the larger of the two small rings, would be observed, since the concentration of radium-12' relative to that of actinium-1 is very small. This would explain Prof. Joly's unnamed halo, the single ring of which has a radius of about 10 . Similarly, if lead alone were isolated from a thorium mineral, the smaller of the two rings would be farmed. This would qxplain the hibernium ring. If protoactinium were isolated, the resulting haloes would have rings characteristic of protoactinium and its products without either of the smaller rings. This would explain the majority of Z1- and Z2-haloes. If lead and protoactinium were simultaneously isolated from uranium minerals, the resulting haloes would show the rings of protoactinium and its products and the larger of the two small rings. This would explain the X-haloes. If, finally, the uranium minerals contained thorium, as many of them do, there would be, in addition to the actinium rings, the smaller of the two small rings. This might explain the remainder of the Z1-haloes. I do not stress these identifications at the moment, but I submit that the two points stated above afford a solution of these unidentified rings more probable than the ascription of Z-haloes to undiscovered and unlikely radioactive products and, as S. Rosseland (NATuRE, 109, 711; 1922) suggested, of hibernium to an element of atomic number approximately 40.If these views are correct, the disintegration series are partly extended to the element mercury; hiberniumn is identified as thorium-2 (or one of the two thorium-2's); the half-value Period of actiaium-! calculated from Geiger and Nuttall's relation is of the order of 1016 ve

ISSN:0028-0836    

DOI:10.1038/120545a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

AFTER the War, extended herring investigations were commenced at Cullercoats, and since 1919 there has been a continued series of observations as to the size, age, sexual development, and growth of the fish from some of the most important shoals in British waters. It is possible to point to three well-defined changes in the shoals and the evidence from growth data indicates that these have been brought about by migration. There is a possibility that these migrations have been due to hydrographic conditions.Towards the end of 1920 there was a movement of some of the North Sea herrings to or towards oceanic conditions, This movement was continued in 1921, in which year the whole of the east coasf fishery was a failure (Reports, Dove Marine Laboratory). The years 1 920—2 1 were marked by an abnormal invasion of Atlantic water into the North Sea. In 1923 the migrants of 1920 21 returned as spring spawners to the groumls off the north of Scotland and about the Shetlands; some few made their way so far south as the Berwickshire coast. Their scales showed a North Sea growth for the first three years and an oceanic growth for 1921—22. In the same year old fish, six winter rings and more, practically disappeared from the shoals of the north of Scotland, Shetlands, East Anglia, and north-west Ireland; the scales of fish from Howth, the Smalls, and St. Ives indicated extended migrations (ibid.). The white fishery was poor on practically all our fishing grounds. Johansen directs attention to an abnormally strong inflow from the Skager Rack to the Kattegat in the spring of 1923 (Jour. Con. Per. Inter. Explor. de la Mer, vol: 1, No. 2) and to increased catches of mackerel from Danish waters (Mecici. Komm. Havund., Fisk, Bd. 7, No. 8). Watkins, in his report on Cardigan Bay shoals, quotes Lloyd as to the invasion of Cardigan Bay by oceanic forms in the summer of 1923.In January 1926, extraordinary numbers of young fish (1924 year-class) appeared off north-west Ireland, and trade papers reported the invasion of the lochs of western Scotland by shoals of small size and poor quality. About the north of Scotland, the 1920 year - class and younger fish failed to appear in sufficient numbers to make anything but a poor spring fishery, and the same applies to the Berwickshire coast (Repts., Dove Mar. Lab.). In August there was an exceptionally good fishery off the Northumberland coast. Following this we have to note a marked difference between the shoals of north-western Ireland and northern Scotland in the early months of 1927. Previously the relative values of the different year-classes were the same for these grounds, but now the 1923 year-class is predominant about northern Scotland and that of 1924 about north-western Ireland. In Shetland waters the year- classes which had been good previously are now poor, and the poor year-classes are good. This is illustrated by the age composition of two samples given below. WINPER RINGS (PERCENTAGES).Bate. 3. 4. 5. 6. 7. 8. 9. 10. 10+ Total. Feb. 7, 19213 , . 12 2 4 35 7 Sf1 8 1 178 3lar., 1927 . . + 36 7 17 5 21 8—1 190 The Northumberland shoals have been marked this year by abnormally high percentages of fish with 2 winter rings. They are a year younger than usual. Reports from friends in the herring trade state that from Wick to below Scarborough the fish have been small. It will be of interest to see if the East Anglian fishery is marked by large numbers of young fish in October and different relative values of the older year groups later in the season.It is evident that the herrings have been swimming differently and the large catches of salmon off the Tyne 1926 27, and the taking in August off the Tyne of cod more than 40 lb. when gutted, suggest that other fish have been doing the same. The Dana in August 1926 took 297 larval eels from the southern part of the Faroe-Shetland channel, and Schmidt (Jour. Con. Per. Inter. Explor. de la Mer, vol. 2, No. 1) gives these an age of 21 to 2 years. The International Ice Patrol reported for 1924 an absence of ice and fog, warmer water than usual 50 to 6 F. above normal in March over the Grand Bank Region, and for the first time a complete cessation of the flow of Arctic water southward along the east side of the Bank during the ice season. The Annual Report, Department of Marine and Fisheries, Newfoundland, 1924, states that Labrador cod were on the grounds before the fishermen were ready, and that whilst the southern Labrador cod fishery was poor, that of northern Labrador was excellent. Huntsman (The Ocean around New- foundland ") records exceptionally warm water over the Grand Bank early in the season of 1924, cod farther in than usual on the banks off Nova Scotia, large quantities of haddock close inshore off Nova Scotia and New Brunswick, the failure of the cod fishery of the Belle Isle region, and the capelirs farther north on the Labrador coast than ever before. Jensen (On the Fishery of the Greenlanders;) records for 1924 the presence of great quantities of large cod in Davis Strait in June, great shoals of small cod off western Greenland at the end of summer, and for the first time in seventeen years the presence of Gadus virens in Greenland waters. From the statistics of the cod fishery given by Jensen, it would appear that in 1924 the cod population of western Greenland split, one half going north, the other south.There is evidence that in 1924 the fish of the north- western Atlantic were swimming differently and that their movements were influenced probably by hydrographic conditions. The connexion between the happenings on the other side of the Atlantic in 1924 and changes in British waters, indicated by the herring shoals as beginning early in 1926, is perhaps worthy of consideration. At present the chain of events would appear to be as follows: An abnormal activity of oceanic waters in 1920 21 probably due to lunar influence; a cumulative effect or a rebound from the Arctic accounting for the happenings of 192:3; the production of a mild Arctic winter, 1923 24; a diminution of cold currents entering the north-west Atlantic in the spring of 1924, followed by changes in the north Atlantic warm currents which influenced British waters and fisheries early in

ISSN:0028-0836    

DOI:10.1038/120546a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE examination of thin sections of coal with the petrological microscope (see NATURE, Dec. 25, 1926, p. 913) has been extended to Tertiary coals from Baluchistan, the Punjab Salt Range, and Assam. The observations previously made on Pahæozoic coals have been confirmed by the later investigations, except for the pleochroism, which is deceptive and probably not actual.In every section which has been studied in ordinary transmitted light, practically all the bright coal and much of the dull coal layers seem to have the structure of polished wood and to consist of a madder—red coloured, translucent substance. If the section is thick or the illumination feeble, this substance is darker coloured or almost black. In very thin sections or with strong sunlight, this substance has a distinct golden yellow colour. Examined in plane polarised light, all sections show an exceedingly faint waxing and waning in the illumination of the coal substance throughout the movement of rotating the section. There is no definite darkening or lightening as a whole at certain positions, and thus pleochroism is evidently absent. Sections of bright coal cut parallel to the plane of lamination and examined between crossed Nicols show the coal substance to be isotropic. The section, although dark, is not absolutely dark between crossed Nicols. Close attention, while rotating the section in this position, shows that every part of the substance goes absolutely dark at some point, but it lets a little light through in other positions. The total light coming through is, however, small, and the darkened section seems to be uniformly darkened even during the rotation of the slide. There is of course the same very faint continuous waxing and waning during the rotational movement, as was noticed for the illuminated section in plane polarised light.All sections cut perpendicular to the planes of lamination and examined between crossed Nicols show the coal substance to have the crystalline character of a uniaxial mineraL The whole of the coal substance seen in the field of the microscope is in optical continuity as if parts of a single crystal. It has, on rotation of the section, a definite extinction, very distinct with really strong illumination, parallel to the lines of the lamiiue. The extinction is not absolute at its darkest point, nor is the section very bright when the Nicols are at 45° to the lamine. However, there is no doubt whatsoever about the extinction phenomena being quite clear in all the sections cut perpendicular to the coal lamime. The coal substance is seen to be somewhat granular under higher powers of the microscope. In some portions of the slides there is evidence of a cellular or woody structure. The presence of recognisable structure in the coal substance does not affect the optical phenomena at all. If a honey-comb was filled with opaline silica and a section made, the general appearance of the slice under the microscope would probably be similar. Stopes and Wheeler (" The -Constitution of Coal," Department of Scientific and Industrial Research, 1918, pp. 20-2 1) have recorded an observation of this nature in the case of a piece of fossihwood examined by them. The siliceous matter had permeated and filled the wood cells without destroying or replacing the tissues separating the cells of the original wood.In addition to the main or chief constituent of coal, the section reveals the presence of three types of minor constituents: (1) Resinous bodies, (2) amorphous mineral charcoal,' and (3) inorgauic matter. Any one or more of these three minor con- stituents may be present in abundance and impart distinctive character to the coal, e.g. dull waxy spore coal (bog head), dull silky coal, and coal shale being types respectively. Each of these minor on stituents offers an attractive field for research. Their study is far more complex than the simple names suggest. The discovery that the chief substance or con- stituent in ordinary coal was probably liquid or fluid jelly which has afterwards hardened affects the existing nomenclature of coal constituents. Notrms based on lithological characters (e.g. vitrain, clarain, and durain) or on a botanical origin (e.g. anthraxylon and attritus) can have more than a descriptive significance. Such names may be convenient if restricted to the appearance or structure, respectively, of the cdal, and not extended to the nature of the coal substance. The older, well-known terms, bright coal, dull coal, and mineral charcoal, with perhaps the introduction of such adjectives as silky, glossy, matte, waxy resinous, and shaley, can be made just as explicit any of the above terms for descriptive purposes. (See descriptions by Fermor, Memoirs, Geological Survey f India, vol. 41, pt. 2, 1 914, pp. 180-181.)A note of warning must, however, be sounded regard to the naming of the chief constituent of coal. It is as certain as can be that this constituent per- meates the coal and has crystalline properties suggestive of a definite substance. We are under delusion that analyses of the purest forms of brown coal, bituminous coal, and anthracite clearly indicate a loss of carbon dioxide and methane from a composition, say, of dopplerite. There is little doubt that with loss of volatile matter the coal substance has not merely hardened, become denser and changed appearance (lustre), but that there is an evident change in composition. Therefore in giving a name to this chief constituent we must remember this change of chemical composition. It would be simplest for the present, perhaps, to use the word coal substance, in a strict scientific sense, for the chief constituent coal, using the general word coal as it has always been u

ISSN:0028-0836    

DOI:10.1038/120547a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

WHATEVER the mechanism of the electric arc, we can scarcely expect an arc to strike and to persist under pressures so low as to render difficult the passage of a high voltage discharge. However, in the course of some experiments on the discharge of electricity through gases, it was observed that under certain conditions an electric arc carrying many amperes can be maintained in a vacuum as high as 0.001 mm.The electrodes A, B, and C (Fig. 1) are placed under a large bell-jar of 12 litres capacity. Electrode A is a heavy rod or block of metal enclosed in B, an electrode in the shape of a box made of heavy metal gauze or perforated plate. Electrode C is composed of a circular plate and an insulated platinum strip stretched across an opening in the plate; it may be used either as a cold electrode or as a Wehnelt cithncle. Electrodes A and B can be connected to the 230 volt line, and electrode C to a source of high potential. When a vacuum is produced under the bell-jar and a high voltage discharge passed between O and B, an arc strikes between A and B and keeps going after the auxiliary discharge is stopped. The higher the vacuum, the easier the arc starts. At 0001 mm. pressure, a p.d. of 60 volts across A and B is sufficient to start the arc, at 005 mm. 120 volts is necessary, while at 1 mm. pressure a p.d. of 230 volts is not sufficient, During the passage of the arc the pressure under the bell-jar naturally increases, but if the electrodes A, B, and C are previously freed from the occluded gases by a prolonged discharge and the moisture in the vessel removed by phos. phorus pentoxide, this increase becomes very small. In one experiment, for example, an arc carrying 3 amperes for 10 seconds raised the pressure to only 0002 mm., and at this pressure, after the arc had been interrupted, the high voltage discharge from electrode C still passed with difficulty, showing the characteristic green fluorescence on the walls of the bell-jar. The fact that with small potential differ- ences practically unlimited currents can pass between electrodes A and B, while the low pressure makes it almost impossible for the discharge to pass from the electrode C in spite of the high potential applied, is very surprising, and indicates that the mechanism of the electric arc is radically different from that of an ordinary discharge. The arc has been produced with copper, brass, iron, and aluminium electrodes. It shows the usual current-voltage characteristic, the p.d. across the electrodes dropping to about 20 volts when the current is increased to 30 amperes. When the are strikes, a brilliant spot appears on the surface of the cathode and continuously changes its position as in the case of a mercury arc.An interesting feature of the arc is the unilateral relationship which the polarity of the arc must bear to the polarity of the auxiliary discharge between C and B. If C is an anode, the arc strikes independently of the direction of the field between its electrodes A and B, but when C is used as a cathode the arc strikes only when A is the anode in the arc circuit. This property of the arc has been successfully employed in some experiments in Fm. 1. rectifying alternating current.

ISSN:0028-0836    

DOI:10.1038/120548a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature