摘要:

SIR WILLIAM CROOKES'S disturbing pronouncement, made in 1898, on the subject of the approaching failure of -the world supply of wheat for lack of coHAkjpef'iiitrogen, lives in the memory of maiiyYV^rJe we to go hungry and to know the tria*pf (scarcity? " fyd asked, and added, " those pre""it 'who^/fnW affifehd/the meeting of the British Associfttiira^Thirty years hence will judge how far (mj forecasts are justified." Naturally, a negative answer to his question was given at the British Association meeting last year, but had he said " sixty years hence," no one would have dared to give a confident reply. On the other hand, his prophecy in regard to the manufacture of combined nitrogen has come true. Led by Germany, nearly every civilised country in the world is actively producing synthetic fertilisers. Now, it should be noted that Crookes confined his attention to the need for nitrogen in the production of wheat. Recent events in the agricultural world, however, justify some consideration being given to a-wider aspect of the nitrogen problem; for, as a recent writer has said, the sum total of life upon this planet is limited by the amount of available nitrogen in combination; important as wheat is in human dietetics, the supply of meat is equally vital. The farmer everywhere is in fact engaged in the manufacture and marketing of combined nitrogen in one form or another. He buys nitrogen in the form of manures and feeding stuffs, and markets it again as corn, meat, or milk. He makes nitrogen when he sows clover and other leguminous plants; and he conserves it for future use when he lays his land down in grass. Under ordinary farming conditions in Great Britain, meat and milk are not produced by grass alone. Intensive farming requires that animals shall be fed on concentrates, that is to say, foods rich in nitrogen, and the use of such foods has two advantages: the protein they contain goes in part to make meat or milk, while the portion not digested, as well as that eventually rejected as waste, goes to enrich the soil. It follows that intensive agriculture in the last analysis involves a process whereby foreign nitrogen is brought on to the farm, is converted into products such as corn and meat, again, in part leaves the farm, and in part is added to the soil. We have, therefore, two stages in the exploitation of land for the production of human food, one typical of the apical development of medieval farming, in which the soil of a locality produces the maximum of human food by the united efforts of Nature and the farmer, and the other, typical of farming after the discovery of artificial manures and feeding ' cakes,' in which nitrogen in one or other of two forms is brought on to the farm from outside, subjected, in part, to a conversion process and added to the sum total of home production of food. It may be noted, too, that the purchase of foreign feedirig stuffs is merely a transference of nitrogen' made ' by natural agencies from one portion of the globe to another. In the case of ordinary nitrogenous manures, also, Nature plays a leading part; ammonia salts are waste products of coal consumption: sodium nitrate from Chile is believed to come fundamentally from the excreta of sea-birds, and others, such as blood, bones, etc., are in the same category.Since the days of Crookes's vaticinations, however, we have entered on a third stage. Agriculture is now drawing on a purely artificial and non-natural source of combined nitrogen, one that makes no call on the resources of the soil elsewhere, or on the natural agencies by whioh atmospheric nitrogen enters into combination. " The fixation of nitrogen," said Crookes, " is one of great discoveries awaiting the ingenuity of chemists. . . . It is vital to the progress of civilised humanity. . . . Unless we can class it among certainties to come the great Caucasian race will cease to be foremost in the world, and will be squeezed out of existence." The hoped-for discovery has now been made. As a recent writer has said, " It is now the era of nitrogen plenty." The estimated world production of combined nitrogen is now about one and a quarter millions of tons, and it is increasing rapidly year by year. But how does the production of combined nitrogen affect human food? Crookes answered the question so far as wheat is concerned. What about meat and milk? It is obvious that if meat is produced by the feeding of a cereal (such as oats) to animals, an abundance of synthetic nitrogenous fertilisers should cheapen the production of meat. But, as matters stand, the cost of meat is governed by the price of the pasture-fed animal jilus the cost of purchased foreign foods. In favoured regions in Great Britain it is possible, no doubt, to fatten an ox on home products alone, but in any event the store animal, that is, the animal before it is ' finished ' for the butcher with albuminoid and fatty foods, is a product of grass lands. It follows, then, that if we could invariably feed a cow, or finish an ox or sheep on grass alone, we should relieve the farmer of a big item of cost- that of cake and corn purchased outside the farm. We have, then, narrowed the problem to this. Is it possible by the use of synthetic nitrogenous fertilisers so to improve our pastures that they will be capable of fattening the meat-producing animal? Science has something to say on the subject-and something new. Research on animal nutrition, led by Kellner, the well-known German worker, has been proceeding for more than a generation. Grass in the form of hay has not been overlooked. Its energy value, its starch-equivalent, have been determined: its practical feeding value for maintenance, for production, either alone or in combination with other foods, has been ascertained, but until quite recently its precise value in pasture conditions was unknown. Scientific knowledge has, however, recently made a great advance. Workers in the Cambridge School of Agriculture have proved that young pasture, grass, that is, grass before any lignification of the tissues has set in, is entitled to rank as a concentrated food, both in respect of protein content, digestibility, and starch-equivalent. Its dry matter actually contains so much as 25 per cent, of digestible protein and 75 per cent, of starch-equivalent. Further, being the natural food of herbivores, we may assume that its mineral and vitamin contents are properly balanced. So that now a scientific view of the subject warrants the confident statement that if the farmer can supply his milch cows and fattening animals with an abundance of young grass, he can reduce the purchase of extraneous foods. Further, as a means of producing that abundance, he can use synthetic nitrogenous fertilisers; and this is not simply a paper philosophy. During the past two years the theory has been tested in Great Britain on a number of farms (including that at Melchet Court, the property of Sir Alfred Mond), and it has been demonstrated that, provided pasture land is kept closely grazed and that growth is continuously stimulated with nitrogenous and other manures, animals can be kept in healthy productive condition for six months in the year on grass alone. Moreover, and this is important, the number of animals which can be so kept on a specified acreage is greater than that possible by ordinary farming methods.Of course, productive animals cannot be kept on grass all the year round; at the most they can be so kept for six months in the year, and in any case the practical farming problem presented by the new scheme is far from simple. Under any conditions grass does not grow at a uniform rate during these six months, and consequently a problem of management has to be faced which, for its solution, may necessitate both feeding for limited periods with foreign foods, and the setting apart of an area of grass land for hay in the standard way. Two further scientific problems also await solution-one, for the plant-breeders, is the making of plants capable of producing a growth of herbage during part of the winter months; the other, for the engineer, is the feasibility of cutting grass in the young condition and preserving it during the winter. A solution on the former lines does not appear to be likely, but the possibility of the second solution is well in sight. The leading producers of synthetic ammonia in Great Britain are actively engaged in exploring the whole problem. (See, for example, "Farm Notes," issued by Messrs. Nitram, Ltd.) They have in operation an extensive series of field trials of which the object is to test the new system of rotational grazing of grass treated with combined nitrogen: they are also at the present time making a cake of dried and compressed young grass, and feeding experiments with this substance will be initiated in the coming autumn and winter.An approach is therefore being made to the complete realisation of Crookes's dream, namely, that the requirements of the country for combined nitrogen shall be satisfied within the country itself -that our imports of that vital requirement shall be reduced to a minimum. Be that as it may, it is satisfactory to know that, as a result of the enterprise of thelatestof the great industrial corporations, a further exploitation of the nitrogen problem, as envisaged by a great man of science, is being undertaken.

ISSN:0028-0836    

DOI:10.1038/120069a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

A MELANCHOLY interest attaches to this paper, the last from Kammerer's pen, which was published only a few months before his tragic death last year. Like his other publications, it is based entirely on work done before the War; for since the War, owing especially to the socialism which became rampant in Vienna, the University of Vienna has become so impoverished that it was unable to pay any but starvation salaries to its staff, and Kammerer left its service and supported himself by journalism and popular lecturing from 1924 until his death. In 1909 and 1911, and again in 1914, Kammerer made a prolonged tour amongst the Adriatic islands, visiting in all fifty of them. The size of the islands varied from tracts of country equal in area to the Isle of Wight to mere islets a few hundred yards across and rocky ' skerries.' The object of these excursions was to find out whether distinct races of continental species of animals were to be found on these islands; and if so, how they were related to their nearest allies on the adjacent continent. As he himself says, his purpose was to follow in the footsteps of Darwin and Wallace, and to glean from the study of these island races light on the origin of species.A preliminary investigation convinced him that the most suitable animals for his purpose were lizards, for these abound in all the islands. Seven species in all were found, namely, two geckos, Tarentola mauretanica and Hemidactylus turcicus, one ' blind-worm,' Ophisaurusapus, and four species of Lacerta, namely, L. major, L. oxycephala, L. serpa, L. fiumana. Of these seven species, however, Lacerta major (which is a large form, 18 inches to 2 feet long) and the ' blind-worm' Ophisaurus showed no variations; Tarentola has the habit of clinging to ships and driftwood, and so owes its wide distribution to human agency. Kammerer's attention was therefore concentrated on the remaining four. The gecko Hemidactylus is a nocturnal or at any rate a crepuscular species, and Lacerta oxycephala confines itself almost exclusively to bare rocks. The other two, L. fiumana and L. serpa, are, however, diurnal and frequent herbage and brushwood, and it is they which show marked variations in the different islands, and it is from the study of them that Kammerer obtained the most light on the problem which he sought to solve. These two species, according to Kammerer, are ' good ' species: he says that the experienced naturalist never mistakes the one for the other in the field, but that when their diagnostic characters are masked by 'superimposed ' island ' characters they are difficult to distinguish. L. serpa inhabits the whole of the Italian peninsula and L. fiumana the whole of the Balkan peninsula, but the line of division between their territories runs along the Balkan coast, so that several large islands there fall to the share of L. serpa; and, curious to relate, it sometimes happens that an island is occupied by one species and the rocks around it by the other. Kammerer has some speculations as to the geological causes of this irregularity of distribution, but they are outside the scope of the subjects with which this review has to deal. It should be noted in passing that Boulenger regards these two species as local varieties of Lacerta muralis. and with this opinion the reviewer, after inspecting the types at the British Museum, is inclined to agree; but whether they are considered as true species or varieties is entirely irrelevant to the question at issue. Their territories never overlap: even in the rare cases where they are both found in one of the larger islands, the areas which they respectively inhabit are separated by a ' lizardless ' band of country.Both L. sfirpa and L. fiumana give rise to well-marked island varieties, and the most marked of these are found in the smallest islands. In the larger islands it is only possible to find distinctions between island and continental populations by the statistical method: isolated individuals often turn up with peculiarities which become constant and universal in the populations of the smaller islands. These smaller islands, therefore, constitute the crux of the problem, and in endeavouring to account for the production of the strongly marked varieties found in them, Kammerer is approaching the problem of the origin of species from the same viewpoint as did Eimer long before him; for Eimer began his investigations into the causes of evolution by finding and describing a distinct ' variety ' or species of lizard on one of the Faraglioni-the rocks in the neighbourhood of the island of Capri in the Bay of Naples. These varieties differ from the type in colour, size, and shape. The colour of the type is green or greyish-green, with longitudinal rows of dark patches on the back and blue ' ocelli' in various places, such as the armpits and the underside of the throat. The colour below is yellow, sometimes with a reddish tinge, or pale grey. The island varieties can be jet-black, so that markings are not distinguishable from the background; they may be half as long again as the type and broad in proportion, and the tail is marked by a peculiar thickening just beyond its origin.That isolation is an all-important factor in the production of varieties is clear from the fajct that when two populations on the same islet are separated by some barrier which prevents them from intermixing, incipient differences make their appearance. Thus in the islet of Taj an there is a deep valley with perpendicular sides which completely separates the lizards of the eastern half of the island from those of the western half, since no L. serpa will ever climb downwards. The eastern lizards show in the male sex a red coloration on the belly, whilst in the western half both sexes show it. Granted that isolation is a pro-requisite for the formation of a new variety, it can only act by preventing cross-breeding, and the question remains to be answered-is it chance variation accompanied by natural selection, or is it the direct action of the environment that is the effective cause of the change 1 Kammerer first examines the case for natural selection. If the black colour is protective, against which foes does it protect? The main enemies of the young lizards are the older lizards, rats, crows, and snakes. But the young in most cases, as on the islets Porno and Melisello, show ' considerable traces of the ancestral colouring and only attain full blackness as they grow up, when the first of the enemies is no longer effective. Rats are nocturnal and hunt by scent, and are only found in some islands. Crows only visit islands near the coast, and snakes only occur on a few of the islands. Seagulls never attack lizards, which have, as a matter of fact, established a kind of symbiosis with them, for the lizards haunt the nests of these birds and search the plumage of the nestlings for parasites without molestation; at the end of the nesting season the lizards are plumper and in better condition than at any other time.On the other hand, Kammerer was able to bring proof that the melanism is due to the direct action of the environment and principally to one factor in it, namely, radiation from rock surfaces. Here he anticipates and answers an objection raised by many naturalists (amongst them Prof. Graham Kerr in his recent book on " Evolution ") that only work in the field can detect the causes of evolution, since experimental- work, under laboratory conditions, can give no idea of what goes on in Nature. Kammerer replies that field observations can give suggestions as to the causes of evolution, but that the validity of these suggestions must be controlled by experiment. Now Kammerer shows that healthy young Lacerta serpa of typical green colour can be rendered quite dark if exposed for 1J to 2 years to strong radiation reflected from stones. // such a pair in middle life are transferred to normal conditions and allowed to breed, they will produce normal green young, but these when they grow up under typical conditions nevertheless repeat a certain portion of the parental darkening. From every island which Kammerer visited, never fewer than twenty and sometimes as many as fifty specimens were sent home to Vienna and there made the subjects of experiments.The experiment just referred to is only one of a number of which Kammerer gives an account, and they leave no doubt in the mind of the unbiassed reader that Kammerer has fully proved his point. As to the causes of the increased size and the thickened tail, Kammerer freely confesses that he has only surmises; since in the few generations he was able to rear, before the War interrupted his labours, he was unable to analyse their causes by experiment. He thinks that both are cases of over-compensation following respectively on starvation and injury. The black lizards go through seasonal orgies of abundant food, alternating with periods of starvation; and the loss of the tail, owing to mutual quarrels on the islands, is so frequent that the lizards are known to the natives, not as black-that is taken for granted-but as the lizards ' of many tails.' Not only did Kammerer blacken green lizards by exposing them to dryness and radiant heat, but he recalled the black lizards of Melisello to their ancestral green colour by keeping them for two generations in a cool and moist atmosphere. He analyses the anatomical bases of the colour. There are three pigments-a yellowish-red lipo-chrome, melanin, and lastly guanin, which produces the blue colour by interference effects. The green is due to the combined effect of the guanin and lipochrome. He shows that as the temperature of the vivarium is increased, first the lipochrome and then the guanin is destroyed, and the melanin extends its range. This state of affairs is reached at 37° C. As the temperature is increased to 39° C., which is the utmost that the lizards can stand, the melanin disappears and a bleached albino results.The response to radiant heat varies from species to species. L. serpa responds more quickly than L. fiumana. The more a variety is accustomed to heat in its natural habitat, the more slowly it responds to increased heat. The southern populations of L. fiumana are extremely resistant-it looks as if they had acquired an ' immunity ' recalling the immunity produced by vaccination. Kammerer of course does not deny the existence of natural selection, but he insists that what is selected is not the random variation in a lucky direction, but the individual that responds best to the environment. Variation, he says, appears at first sight to be random, but when it is looked into closely it is quite orderly and consists of plus and minus variants on a typical mean. There are different systems of organs which he mistakenly compares to the Mendelian genes, which react independently of one another. Thus in some varieties of lizard, blackening is attained by the appearance of melanin in the background; in others the black patches of the pattern spread until they overwhelm the background. Further, lizards and snakes, like amphibia, have the power of adapting their colour pattern to that of the environment, and this power is exercised through the eye. It is a question of a delicate balance of stimuli whether this power, or the direct response of the skin, shall gain the upper hand. In the islet of Pelagosa, for example, which is covered by a yellowish-green vegetation, L. serpa is bright green but the snake Zamenis is represented by an intense melanic variety. The gecko Hemidactylus has a particularly mobile response to its environment by change of colour, recalling in this the well-known chamseleon; yet even here the environment makes an impress on the hereditary constitution, for there is one islet where, owing to the absence of Lacerta, this species has become diurnal, and Kammerer ascertained by keeping this variety alongside of typical specimens in the same vivarium in Vienna that the responses of variety and type to the same environment were different. Kammerer maintains, in fact, that the first step in the formation of a variety is a continual heightened response in the same direction which gradually become engrained in the constitution. " Physiological change precedes morphological change." L. oxycephala, as mentioned above, frequents bare rocks and, unlike L. serpa and L. fiumana, will descend as well as ascend. This species has given rise to a black variety on the upper arid slopes of the mountains of Herzegovina (L. oxycephala Tomasinii}, where the lizards are exposed to pitiless radiation. Thus a variety can originate just as well on the mainland as on an island if intercrossing with neighbouring, groups isj prevented.We may in conclusion say |iword on the addendum by Dr. Wettstein. This is?in admirable systematic review of the Kammerer material. He establishes several new sub-species on the basis of this material, and he mentions the fact which has a direct bearing on the causes which broke Kammerer's heart and drove him to suicide, namely, that a good deal of this material had lost all its colour and was hopelessly macerated and ruined when he came to examine it, by neglect in the museum during and after the War. The reviewer is aware that he speaks for only a small minority of his colleagues, but he predicts that in twenty or thirty years' time, when those fierce partisans whose calumnies wore out Kammerer's courage and drove him to his death, have passed away, Kammerer will be ranked alongside Lamarck, Darwin, and Wallace as one of the great architects of evolution. Really, when one passes from perusing the endless and fruitless pursuits of the elusive gene by the Mendelians, to reading the clear arid beautiful arguments of this work, one has the feeling of having passed from the babbling of the nursery to the reasoned debate of the foru

ISSN:0028-0836    

DOI:10.1038/120071a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE title of this book at once raises the question of what is a founder. For Dr. Davison the answer is simple; he is any one who is no longer living. Yet a different point of view might be adopted, for, if an architectural metaphor is to be used, the history of few branches of knowledge can be divided more readily than seismology into the two periods, of laying, the foundations and of building the superstructure. The limit between the two periods lies in the first decade of the present century, and may be more precisely fixed at the time of the Californiati earthquake of 1906. Subjected to elaborate investigation and a sumptuous publication of results, the increase of knowledge and the precise measurement of effects, which had only been recognised in a qualitative and even uncertain way, was very largely instrumental in inspiring a change in our outlook on the fundamental principles of both the old and the new seismology. Earthquakes have been a subject of study from early times, but the science of seismology, in its more modern sense, ijid not begin before the eighteenth century, and by the' middle of the nineteenth the main principles had been established on which all further work has been based. So far, however, the science had only dealt with the. seismos which was known to and studied by the ancient Greeks-that is, the disturbance which can be felt, which may cause damage or destruction to the works of man, or may alter the features of a landscape, according to the degree of violence attained, but in the last decade of the century a new seismology was born. The incarnation of this new science may be dated from the discovery, by Rebeur-Paschwitz, that records could be obtained, with suitable instruments, of disturbances, evidently connected with destructive earthquakes, at places far beyond the region in which even the feeblest manifestation of the work could be detected by the unaided senses of man; and by the beginning of the following century it had been well established, and generally accepted, that these ">distant records revealed the existence of three distinct forms of wave motion, travelling at different rates and along different paths, from the origin to the place of record. This is the foundation on which has been reared the whole superstructure of that newer seismology which has shown us that the earth is composed of a series of concentric shells of materials, differing in physical character and, presumably, in chemical composition; which has given rise to investigation of the character, and revealed the existence of previously unsuspected forms, of wave; and to other results which only a generation that has forgotten, or chosen to ignore, its Greek could describe as seismology, but are equally interesting and important by whatever name they may be called. Nor has the older seismology stood still. The report on the Californian earthquake of 1906 still belongs to the period of foundation-laying. The work was dominated by the idea of a centre of origin, though this was no longer regarded as of such limited dimensions that it could be treated as a point; it had become a fissure extending for a length of nearly 300 miles, but was still regarded as the origin both of the destructive earthquake and of the distant records. The cause, too, was regarded as the shock resulting from fracture, due to a slowly growing strain, which had gone on accumulating, with occasional partial relief, for a period of at least a century. A re-examination of the record of older earthquakes, and the study of more recent ones, has altered this; it has been found that, in destructive earthquakes, the origin of the surface shock is not so simple as had formerly been supposed, that instead of being a single fracture, or limited to the central portion of the affected area, the origins are often very complicated and spread over a large proportion, even to almost the whole, of the tract over which the shocks can be felt; it has also been found that the origins of the surface shock and of the unfelt distant record arc by no means the same. The destructive earthquake can be proved, by local observations, to be of very shallow origin, generally, if not always, of less than ten kilometres in depth; and the same is true of the great majority of shocks which can be felt but do not cause damage or give rise to distant records. The disturbance which is registered at long distances has been shown, by the great series of observations studied, especially by Prof. H. H. Turner, to originate at depths which must be measured in hundreds of kilometres, and the examples are steadily increasing in number where the geographical position of the origin of the long distance records does not agree with that of the greatest violence of surface shocks, but may be at a considerable distance, even to a hundred miles or more. Yet the two are evidently in some way connected with each other, and if we liken the origin of one to the discharge of a great gun and of the other to the explosion of its shell, it is easy to see that the disturbance produced by its own charge of explosive would be very different from that which would result if it happened to strike an ammunition waggon or dump. In this way we may dimly realise the connexion between the long-distance record and the earthquake proper, and may find an explanation of the fact that there seems to be no quantitative relation between the two; a highly destructive earthquake may give a small record, while a much larger one may accompany a disturbance which is only felt as a moderate and harmless shock near the origin.Such, in brief outline, is the scheme on which a useful and interesting book might be written. Dr. Davison, in dealing with the works only of those individuals who are no longer living, has adopted a safer and probably more permanently serviceable line. This course is not devoid of inconvenience, for the end of some has been so recent, in two cases so late as 1923, that their work belongs as much to the building of the superstructure as to the laying of the foundations, and the absence of reference to the work of those still with us leads to a very partial and even misleading aspect of the present state of our knowledge. This, however, forms but a fraction of the work; the rest of it gives us something that was much wanted. A general knowledge of the early history of the subject of his study is useful to every worker, but for each to go separately through the old literature would be an unjustifiable reduplication of toil, which Dr. Davison's work has rendered unnecessary. An extensive and, what is more important, an accurate reader, Dr. Davison has in pre-eminent degree the knack of extracting the nutricious kernel from the husk and shell in which it is clothed, and of expressing clearly those results which are of permanent interest or import ance. He has produced an excellent account of the early history of the study of seismology, which contains what every serious worker at the subject ought, and all that, except for very special research, he needs, to know, of these older works and workers.

ISSN:0028-0836    

DOI:10.1038/120074a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

(I) PROF. BRODETSKY has followed up his -L great success in organising the Newton celebration at Grantham by publishing what is easily the best short book on Newton's life and work. It is really even more than this, for it would be difficult to find anywhere a clearer and more instructive account of the genesis and meaning of the differential and integral calculus, as well as the way in which the law of gravitation brings together and completes the work of Galileo and Kepler. All this is done by a first-rate mathematician with a turn, like his hero, for the practical and applied side of mathematics. To have accomplished this, with a lively narrative of Newton's personal life and all the relevant public occurrences of the time, within a compass of 160 pages, is a remarkable feat, and it is to be hoped that Prof. Brodetsky will go on to employ the talents which he has revealed in this volume by treating some other of the great figures in science in the same way. Nothing could be more stimulating to a young student than to read and re-read this book, mastering the admirably simple diagrams and looking up the - references to contemporary thinkers with whom Newton was in touch. It is, in fact, a model of how the history of science should be presented - short, interesting, personal, suggestive, and competent. It does not attempt to cover the ground of the sciences which Newton studied and advanced, but it illuminates the advance and creates at every point that most wholesome of all appetites - the desire to know more.To the student of general history, the connexions with other contemporary events, with which Prof. Brodetsky rightly and richly sprinkles his pages, will be specially welcome, for they help to build up the growing idea of the unity of history, and they show also how easily and in what small space it may be done, if we set out to do it and have the requisite knowledge. Newton's general philosophy fits in with that of Milton, whose " Paradise Lost " was completed at the same moment as Newton's two capital discoveries; Newton practised jumping with and against the gale in the storm which accompanied Cromwell's death; the first part of the " Principia " was published just as Charles II. was dying, and with the imprimatur of Samuel Pepys; and so on. Une ceuvre de vulgarisation du premier ordre.(2) Close on Prof. Brodetsky's popular account of Newton comes a short Trench book on Descartes which offers other points of interest. M. Dimier, as compared with Prof. Brodetsky, is literary, personal, and, above all, Catholic. His book is beautifully written in a terse, pointed, and unadorned style, and Descartes is a still more unqualified hero to him than Newton is to the English writer. Two capital and connected points are aimed at in the treatment: first, that Descartes' thinking was essentially synthetic and religious; second, that he was primarily inspired in his philosophic work by a desire to combat the popular scepticism of the day.If one makes due allowance for the one-sidedriess and exaggeration of this view, one may certainly gain a good deal of sidelight both on Descartes' work and on the life and thought of his time. It is true-on the first point-that Descartes was primarily metaphysical and philosophic, whereas Newton was primarily mathematical and positive. Newton was above all concerned to make sure of his conclusions with regard to a particular law or set of observed facts. Descartes was from the first seeking to know, and to connect the whole of his knowledge in one coherent and unassailable system. This is in general the difference between the philosophic and the scientific approach, and it may be paralleled in the nineteenth century by the difference in the attitude and the influence of two leading men-again a great Frenchman and a great Englishman - Comte and Darwin. In each case the influence of the philosophic type is more diffused and indirect, and of the scientific more direct and constructive of fresh scientific truth.On the Catholic question which pervades the book before us, it is sufficient to say that while Descartes was never anti-Catholic or sceptical, and conceived his main work to be the establishment of a body of certainties on a deistic basis, yet he certainly did not start from theology but from mathematics. His philosophy was inspired by mathematics, and he feared assaults from Catholic critics -as much as from the Calvinists who got up a great case against him in Holland. On the details of all this and of his correspondence on moral questions, M. Dimier is instructive and interesting, and well deserves to be read.

ISSN:0028-0836    

DOI:10.1038/120075a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

A FURTHER addition to petroleum literature is at the present time almost a challenge to criticism, in view of the voluminous writings extant on every possible branch of the subject; only flagrant heresy and iconoclasm, a brand-new theory of origin, for example, would seem to justify a new text. Though this book claims neither excuse, it is acceptable for three good reasons: that it has been an authoritative German text since 1912, revised in 1924, and now admirably renovated for the benefit of English readers by its translator, Mr. Harold Moore; that it presents the European and not the American viewpoint; and that it is less concerned with commercial oil-refining than with the scientific principles on which that industry thrives. The author holds high academic office at the University of Baku and, as might be anticipated, his writing is coloured with experiences of Russian petroleum and biassed to the work of European colleagues, truly a refreshing departure ofrom recent tendencies. We have here a real text-book of the chemistry and physics of petroleum, two remarkably complex subjects when considered for their own sakes and not for their economic applications; in fact, one of the features of-this volume is its indication of the enormity of unfinished research, of work still to be done, of knowledge yet to be gained, before we can claim understanding. As a text-book it leaves little to _be desired. Carefully arranged, lucid in style, concise in presentation, entirely technical but never fogged with petty detail, masses of formulae or wild speculation, the work makes an immediate appeal and deserves, as it will undoubtedly achieve, a place in the front rank of English literature on the chemical technology of petroleum.The discussion centres on three main factors: raw material, manufacture, and products, each treated from the scientific viewpoint, i.e. the first principles involved. Petroleum, the raw material, is first reviewed and its chemistry and physics explained so far as this is at present possible. Manufacture concerns essentially distillation processes and sulphuric acid refining. The products benzine, illuminating and lubricating oils, paraffin wax, and vaseline are similarly described. While theory and experiment remain uppermost throughout, the rationale of industrial operation is not neglected, but rather follows as an illustration of the doctrines expounded. Deficiencies there are bound to be in a work of this character, but they are for the most part innocuous; the treatment of sulphur and nitrogen compounds is poor in its brevity (pp. 113-119), likewise inert gas components of natural gas (p. 124); the misuse of the geological term ' weathering ' as applied to evaporation of petroleum (p. 175); the data of crude oils of the world are antiquated and there are serious omissions of Mid-Continental and Colombian crudes (Ohio-Indiana is not the accepted Mid-Continent v field): the use of the term ' resin ' (p. 200) for the asphalt-content of Balachany oil is misleading and should not be allowed to confuse an already clumsy and ' muddy' nomenclature; the section on v products is far more sketchy than the rest of the text, especially in regard to the vital subject of lubrication. All this pales, however, by the excellence of the translation and the esteem which one instinctively feels for one who is a master of a particularly complex subject. Prof. Gurwitsch is fully entitled to renewed congratulations.

ISSN:0028-0836    

DOI:10.1038/120076a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

As an introduction to the subject, this book doubt less covers the requirements of students of pharma ceutical chemistry. It does not, however, in matters of detail, arouse the reviewer's enthusiasm. The introduction of unusual abbreviations is confusing; the arithmetical examples are frequently expounded in an unnecessarily elementary manner the use of exactly normal solutions, instead of the employment of a factor" is directed; the explanation of the use of excess of free acid in permanganate titrations is incomplete, so as to be quite misleading; the use of the symbol 03, except to indicate a molecule of ozone, is to be deprecated; the standardisation of jV-sulphuric acid by titrating 10 c.c. with " recently prepared and standardised JV-potassium or sodium hydroxide " is open to obvious criticism. In addition to the usual in organic volumetric exercises, the analysis of sugars, oils, alkaloids, urea, formaldehyde, and organic nitrites is described, and a short section is devoted to the principles underlying the determination of hydrogen ion concentration.

ISSN:0028-0836    

DOI:10.1038/120077b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

NORTHERN SIAM- the Lao country - has received little Wention from travellers, and although the teak'trade has attracted not a few Europeans, information about it is scanty. This is the more to be regretted as it well deserves Mr, le May's designation of ' Arcady,' and its people ethno-logically present many points of interest. This account of the country and its people is therefore welcome, especially as it is illustrated by a large number of excellent photographs. The author has dealt with his subject historically and analytically in an ethnographic account of Lao customs and beliefs, which, though not systematic, contains many interesting data; and descriptively, in an account of a journey through the country. He has also included extracts from the references of early travellers. The first of these is Marco Polo, who, however, did not visit the Lao himself. The Lao were originally an offshoot of the Tai from China, and ethnologically they stand midway between the Shan and the Siamese. Nominally Buddhist, their beliefs are largely animistic, with a firm belief in the power of witches. A characteristic practice is that of roasting the mother of a new-born child, a custom also followed in the Malay peninsula - in ijxfeceiitly reported case with fatal results.

ISSN:0028-0836    

DOI:10.1038/120078b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THIS useful work is a reprint of the technical advice concerning physical lecture experiments given in the introductory volume of Geiger and Scheel's handbook of physics, which has appeared in 24 volumes. It describes 533 lecture experiments covering the whole range of physics. Many of these are new, and in all of them due consideration is paid to the modern resources at the disposal of the experimenter. This applies particularly to the thermionic valve. We notice elegant methods of demonstrating stream lines by means of coloured liquids, the Johnsen-Rahbek effect of friction due to small currents, experiments with the speaking arc, and some very pretty and ultramodern spectroscopic demonstrations. A valuable feature of the book is the addition of the essential definitions and formulae, together with the chief numerical data. As the work is not a text-book of physics, nothing but what is essential to the success of the experiments is given, and given in the smallest compass. But wherever desirable, references to original papers or text-books are appended. Altogether an admirable book.

ISSN:0028-0836    

DOI:10.1038/120079a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE name of W. Weber is one of those outstanding continental names which are associated with epochs in the development of science, and are regarded with honour in Britain. Yet in Britain there has been evident a considerable amount of misunderstanding regarding Weber's initiation of the essential features of the modern theory of molecular magnetism. That misunderstanding seems to have originated in an unfortunate wording of a remark made by Maxwell in his exposition and development of Weber's work (“Electricity and Magnetism”, vol. 2, 2nd ed., p. 76).The two essential features of the modern theory are clearly stated by Maxwell. First he says (p. 74): " Weber's theory differs from this in assxmaing that the molecules of the iron are always magnets, even before the application of the magnetising force." Secondly, he says (p. 76): " The molecules do not turn with their axes parallel to x (the direction of the magnetising force), and this is because each molecule is acted on by a force tending to preserve it in its original direction, or because an equivalent effect is produced by the mutual action of the entire system of molecules." It is the statement in the last clause which contains the second essential feature. In addition, Weber adopted Ampere's view that the molecular magnetism results from molecular currents; and, to this view, modern physics has merely added the restriction that these currents are connective.In the first sentence quoted above from Maxwell., the first feature of the modern theory ia explicitly ascribed to Weber: in the second sentence, the second feature is not directly ascribed to him. If that feature were not due to Weber, that sentence would, in accordance with the rules regulating scientific priority, fix it as the property of Maxwell arid constitute him as the originator of one-half of the essential fundamental postulates of the modern theory. But Maxwell is making no claim for himself. In his next sentence he adds that " Weber adopts the former of these suppositions as the simplest." This last remark clearly points out that Weber discussed the second feature. Therefore, unless he explicitly abandoned it, he was the originator of both of the basic postulates of the modern theory. Maxwell's words do not necessarily mean that Weber abandoned the second supposition. They only assert that he did not follow it out; and, further, that he did not do so because that supposition was not so simple as an alternative which was chosen by him.Now the most minute search of Weber's paper (Pogcj. Ann., 1852), word by word, reveals two facts- (1) Weber not merely, as Maxwell implies, asserts the second feature of the modern theory, he reiterates it again and again; (2) Weber not merely avoids any choice between that feature and another one, for reasons of simplicity or otherwise: he persistently avoids the consideration of any alternative. Therefore he, and he alone, is the author of the modern theory of molecular magnetism.Moreover, Weber was not merely the originator of the fundamental ideas. He was their first developer. No later worker can do more than apply his views more widely. Weber himself illustrated the applica- * tion of these views, in two cases, by a formal development of the action clue to a neighbouring molecule; and that application constitutes one of those gems of intuitive insight which characterise the work of the masters. Therefore Maxwell cannot, in the sentences quoted above, apart from a serious misunderstanding, be ascribing to Weber a choice between a non-magnetic force and one of magnetic origin. That is perhaps the most natural interpretation of his words, yet he does not explicitly mention a non-magnetic, force any more than does Weber. That idea was introduced by other workers.Weber did make one choice, and that evidently for reasons of simplicity as Maxwell said, though lie did not state them as such. In speaking of the force which must be acting so as to drive back a magnet to its position of equilibrium when it has been deflected " from it through an angle t, far from saying a nonmagnetic force, he says, " But this back-acting force, arising from the mutual actions of the molecules, must increase with the deflection, arid can be represented by D sin ft, where D denotes a constant magnitude which one can call the molecular directive force " (p. 166). That is Weber's direct assertion in introducing the very expression for the resultant ffcrce with which Maxwell deals. Therefore, as above stated, Maxwell could not possibly assert or mean that Weber abandoned the view that the force had a source apart from the mutual molecular magnetic interactions. On the other hand, it iS to be noted that Weber's theory fixes the expression for the force whenever the distribution of the surrounding molecules is given. The thing that Weber definitely avoided, and that for the sake of simplicity alone, was the necessarily laborious evaluation of the true expression for the internal field. He took the only other possible method of approved scientific exploration, the method of postulation of a simple and sufficiently approximate expression for it. Maxwell, apart at least from an accidental failure to notice Weber's own statement regarding the nature of D, could mean nothing else than that; but the wording of his statement can unfortunately lend itself to the other interpretation.The incorrect supposition that Weber abandoned the idea of mutual interaction of the molecules by moans of their magnetic fields alone has not been quite universal in Britain. Jeans, for example ("Electricity and Magnetism"), describes the correct position with great clearness. The later development of the subject by Ewing was largely directed towards the illustration, by means of models, of that mutual interaction of molecules which Weber first put forward, and against all postulates of the existence of quasi-elastic forces which had been made by certain other writers, amongst whom, however, Weber is riot to be found.The task of subsequent work is the evaluation of the force symbolised by D. Weber made the most drastically simplifying postulate regarding it. He assumed it to be constant, and found the result to be in agreement with observation in the case of soft iron: and he insistently reiterated the statement that he was dealing only with non-retentive iron. It was Maxwell who pointed out the over-stringent nature of Weber's postulate if retentiveness is to bo taken into account, and he widened it accordingly. That was Maxwell's work, not Weber's, and in it he followed Weber in - tentatively assuming a simple form for the law rather than determining it by mathematical development, which the state of experimental knowledge at the time could scarcely justify. In the more recent development of Weber's ideas the question has been again raised whether the internal molecular magnetic field is sufficient to account for observed phenomena. Thus Weiss, who adopted Weber's assumption regarding the internal field to fit it for application to crystalline media, was led by thermomagnetic phenomena to ascribe very high values to the internal field relatively to even strong external fields. He afterwards pointed out that the high values may include equivalent values of fields which are actually non-magnetic, but may, for example, be electrostatic if the molecular magnet is also an electric dipole; and this view leads to values of the molecular electric susceptibility which are consistent with results of observation.Now an application of Weber's theory to a determination of the actual law of force, due to the mutual actions of the molecular magnets in a homogeneous crystal, readily indicates that the magnitude of the internal field is of the same order as that of fields which are normally used in the investigation of the magnetic properties of substances. It shows, even without numerical evaluation, that the least possible value of an external field which is able to magnetise a cubic crystal in any direction relative to its crystalline structure is equal to five-eighths of the maximum internal field. That is to say, the maximum internal field acting ua molecular magnet is not twice as strong as the external field which is just able to turn the molecular magnets out of their stable directions, and so to magnetise the crystal in any direction. This is true whatever be the nature of the internal directive field which tends to maintain the magnets in their stable positions. If that internal field has in part an electrostatic origin, the remaining magnetic part is proportionately smaller.This is in accordance with the observations, described in a recent issue of NATURE (Mar. 5, p. 353), on the deflexion of j3-particles in their passage through thin magnetised nickel foil. If we postulate that there is equipartition between the average translational energy per degree of freedom of the molecules and the average rotational energy of a molecular magnet, the axis of which is maintained, in consequence of the heat motions, on the average at an angle j with the direction of the resultant field, we find, on evaluation of the internal field, that, at ordinary temperatures, this postulate is not satisfied. The change of potential energy of a molecular magnet, due to the rotational effect of heat motions, amounts only to about 1 per cent, of the energy per degree of freedom. This seems to indicate that the internal structure of the molecule is such that, in the collisional interchange of energy amongst molecules, only about 1 per cent, of the whole is communicated to the subatomic portion of the structure which is concerned with the manifestation of magnetic quality.

ISSN:0028-0836    

DOI:10.1038/120080a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE recent articles by Dr. P. Chalmers Mitchell and Prof. C. Lloyd Morgan (NATURE, May 21, p. 748, and May 28, p. 786) clearly show the increasing importance of the problem of emergence. But it seems to me that Prof. Morgan advances a criterion of emergents which is seriously defective, and so prevents any reconciliation of the opposed viewpoints. In the first place, he appeals to “matters as they now are”, and quite apart from what future discovery may reveal. It follows, therefore, that as knowledge expands, much that is now regarded as emergent may prove to be resultant, since it will become deducible from the phenomena of some “earlier phase”; and to this progress no limits can be assigned in advance.This attitude is plainly an appeal to the ignorance which prevails at any given moment; and it at once destroys any absolute distinction between the emergent and the resultant. Now the trend of research, in my opinion, undeniably involves this loss of absoluteness, as Dr. Chalmers Mitchell maintains. For while it will always be impossible to deduce the macroscopic qualities of combinations from the macroscopic qualities of their elements, the more complete knowledge of microscopic and ultra-microscopic qualities does enable the qualities of combinations to be both explained and predicted. In this respect success depends on the capacity of the inquiring mind; so that as mind evolves, emergents must give way to resultants. If, for example, we accept Prof. Morgan's criterion, then to Galileo electromagnetic storms, due to solar radiation, would be emergent, while to us they are resultant. Similarly, many of the phenomena presented by vitamins, not being as yet deducible, are still emergent, but will probably be resultant for future bio-chemistry. The criterion of being, or not being, deducible is thus wholly relative and transient; and it obscures what I take to be the sole genuine attribute of all emergents, whether deducible or not; that is, uniqueness, or the possession of characters previously unprecedented. From this more inclusive and permanent viewpoint, atoms and crystals emerged, exactly as did life and sentience at still later stages; and this quite apart from the partial, or complete, explanation of their origin. For each of these was, when it first appeared, in its own specific way unique, exactly as " Hamlet " would remain unique even though it could be fully accounted for in terms of Shakespeare's life and character. Such absolutely unique combinations occur, of course, throughout the entire universe, and present one of its most marvellous and significant features. So that although " out of three sounds he frame, not a fourth sound, but a star," still A star's a star for

ISSN:0028-0836    

DOI:10.1038/120081a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature