摘要:

THE greatest public health triumph of the last 1T half-century has been the almost complete conquest over water-borne infections. In Great Britain the chief of these is enteric or typhoid fever; and the reduction of the death-rate from this disease in England and Wales from 332 per million of population in the average experience of 1871-80 to 25 per million in the average experience of 1921-25, shows that this disease is following typhus fever and becoming a disease of rare occurrence in the country. Although reduction of personal infection by better nursing and hospital treatment, the increased protection of foods which, like oysters, are eaten raw, and the help which bacteriology has given in securing prompt diagnosis of enteric disease in 'carriers' as well as in clinical cases of the disease, have all borne an important part in bringing about this remarkable result, the chief factor has been the protection of the public water supplies of Great Britain. The substitution of supplies controlled by municipalities or by large commercial companies for smaller supplies inadequately protected has formed an important element in securing clean water. Although when accidental contamination occursas in the historical Maidstone and Worthing epidemics of enteric fever-the unification of water supplies for large communities may imply widespread disease, the standard of precautions has steadily improved, and the communal supply of water by a single authority in each area has been the chief means for protecting the communities concerned by means of safe drinking water.A very large part of the total drinking water supplied in England is derived from rivers; and its protection necessarily implies serious difficulties. Of the two alternatives, that of keeping the water pure and that of purifying it after contamination so as to render it safe for drinking, the first is obviously preferable; but in most modern communities this is impracticable to the extent which would obviate the need for supplemental purification. In this connexion much interest attaches to the report of a deputation which waited on the Earl of Balfour (on behalf of the Prime Minister) on Feb. 15 last. This deputation represented the British Waterworks Association and the Salmon and Trout Association, and it urged on the Government the need for the creation of a national co-ordinating authority with powers to set up riversand watershed boards for all rivers in England and Wales.This was urged in view of the risks to health of the increasing volume of river pollution, the threat to fish life, and the impairment of the beauty of the country caused by the increasing volume of pollution of our rivers. The facts are not in dispute. There is perhaps ample law to enable pollution of rivers to be controlled; but responsible authorities are inert, or fail to co-operate. Lord Balfour's reply to the deputation took in part the form of most pertinent queries and showed the difficulties of the problem. Is the proposed central authority to have executive powers, and how are these to be related to those of existing authorities ? Leaving administration for science, Lord Balfour pointed out that the essence of the problem consists in the purification of effluents before they are discharged into streams. It is evident that rivers inevitably must act both as sources of water supplies and as recipients both of domestic sewage and industrial waste products. The danger that domestic sewage will cause infectious diseases, and the effect of trade effluents on fish life, form two separate problems, of which the former can be much more easily controlled. As regards trade effluents, there must always be involved a balanced consideration of the expense of complete purification and of the loss implied-to fish life and to Tsthetics-in neglecting it.The deputation should, however, do good. Research has generally shown that purification of effluents is economical to the manufacturer as well as beneficial to the public; there is already in many instances adequate knowledge to secure purification; and the pressure of public opinion as well as the utilisation of existing powers is called for to secure the adoption of measures of purification now feasible. London is the greatest example in the world of a public water supply derived chiefly from sewagecontaminated rivers, which for many years has been distributed daily to several million people without any serious outbreak of enteric fever or cholera attributable to it. This has occurred during a long series of years, in which chief dependence has been placed on sand filtration of the crude river water, and more recently on additional prolonged storage in large reservoirs; and it is a great tribute to the large London water companies in the later years of their experience, and to their still more efficient single successor, the Metropolitan Water Board, that this gigantic experiment on human beings has been so uniformly free from ill results. Under the guidance of Sir Alexander Houston the last-named Board has steadily increased the use of an additional safeguard, and now about 76 million gallons of Thames water are chlorinated daily Since 1916 some 2 millions of people have daily drunk this water after filtration without detecting any difference in its taste. Without entering into detail, it is interesting to note the statement made by Sir Alexander in the twentieth annual report of the Metropolitan Water Board that, judged by bacteriological quality of the water supplied to London, " it would be safer to drink 1000 fluid ounces or fifty pints of some of the stored waters than one fluid ounce of the raw river water antecedent to storage."The steadily favourable experience of the metropolis has some bearing on a report by Dr. Hancock just issued by the Ministry of Health on an outbreak of illness at Poplar suspected to be due to local pollution of the water supply. The illness in question was diarrhoea associated with fever, and between July 11 and 12, 114 cases occurred, and probably many more. Foods, including milk, were excluded, as the result of investigation on well-known lines, as possible causes of the outbreak, and suspicion turned to water as a possible vehicle of infection. The water in the implicated area gave unsatisfactory bacteriological results; and investigation showed that in the special area implicated in the " veritably devastating " local outbreak there existed a complex arrangement of water pipes, those of the local gas works being supplied in part from the River Lea, opposite the gas works, which in this locality is heavily polluted. It is possible that some of this contaminated water had by reflux got into the water mains of the district and thus caused a serious outbreak of illness. Actual proof that such inter-communication of pure and contaminated water had occurred could not be obtained; but the cross pipes have been disconnected, and the report has a high value in directing attention to the possible dangers attaching to such arrangements. Some interest attaches to the bacteriological side of the investigation. No dysentery-like bacilli were identified and agglutinin tests were negative; but, as is pointed out by Dr. W. M. Scott in a. supplementary report, a similar experience occurred recently in Hanover. In the Hanover experience a serious typhoid outbreak followed; fortunately this was escaped in Poplar.The report should be studied by health officers and water engineers; and it reminds us once more that the price of immunity from water infection is uninterrupted vigilance both on the engineering and the chemical side of public health.

ISSN:0028-0836    

DOI:10.1038/119769a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

M R. HINSHELWOOD'S book provides an lMl opportunity for the general reader to make himself acquainted with a branch of chemistry which is developing rapidly at the present time, but of which the importance may not be appreciated by those who do not profess and call themselves physical chemists. These new developments may be summed up in the term 'activation.' This conception has been introduced in order to account for the slowness of chemical change, and in particular for the fact that molecules which are capable of dissociating or of undergoing isomeric change do not do so all at the same time, and immediately, giving rise to instantaneous reactions. This delay can sometimes be traced to the fact that the action is conditioned by association with some foreign substance, e.g. moisture, and that the molecules which wish to undergo change have, as it were, to form a queue and take their turn in receiving the necessary dispensation from the appropriate official; but since even the wettest and dirtiest materials do not change instantaneously, there must be some condition of 'activation 'within the molecule itself which is a necessary precedent to chemical change. An exception to this rule is found in ionic double decompositions, where the ions behave as if they were already activated, and therefore interact as fast as they can come into contact with one another. It is therefore an attractive proposition to associate reactivity with a condition analogous to ionisation, and for this view there is considerable justification in the case of actions which take place in liquid media. But in the case of gaseous reactions, at least, it is probably more to the point to think of activation in terms of energy, and to regard an activated molecule as one which contains a larger supply of energy than its inactive neighbours, since, when once this reserve of energy is created, it can be drawn upon to overcome whatever obstacles may be found to impede the progress of chemical change.Physical chemists claim, however, not only to know of the existence of this process of activation, but also to be able to give a numerical estimate of the degree of excitement which precedes chemical changes of the most diverse character. The most familiar method is to deduce a value for the heat of activation from the effect of temperature on the velocity of the reaction. The relationship which Arrhenius used for this purpose is expressed by the formula, d log k/dT =A/lRT2, where A is the ' heat of activation ' and k is the velocity coefficient at temperature T' abs. This is almost identical with Van 't Hoff's formula, d log K/dT = Q/RT2, whereby the heat of a reversible reaction Q can be deduced from the variation of the equilibriumconstant K with temperature; but whereas Van 't Hoff's formula depends on strict thermodynamical reasoning, and can be tested by direct experiment, Arrhenius's formula is necessarily of a more speculative character, since the hypothetical heats of activation to which it leads cannot be measured by any direct process. The validity of the formula finds some support, however, in the fact that a very accurate linear relationship is revealed in a large number of cases when log k is plotted against 1T. When this relation holds good, as in the decomposition of hydrogen iodide into hydrogen and iodine, or the thermal decomposition of ammonia in contact with a tungsten filament, one is tempted to believe that the 'heat of activation' deduced from it may perhaps represent a real physical property. A similar statement can be made in reference to those cases in which this method of plotting gives rise to two straight lines with a rounded intersection. This characteristic is observed in the union of hydrogen and sulphur, which Norrish and Rideal formulate as depending, in the lower ranges of temperature, mainly on an interaction at the surface of liquid sulphur, and, at higher temperatures, mainly on an interaction in the gaseous phase.The chief interest of Mr. Hinshelwood's book is to be found in his description of a second method for determining the energy of activation. This is limited to gaseous reactions, but has a much stronger theoretical basis than the somewhat speculative relationship of Arrhenius. It depends on calculating, by means of the kinetic theory of gases, the number of collisions which take place in unit time between the molecules of a gas, and then comparing this with the actual number of molecules which undergo chemical change in the same unit of time. This calculation shows that in a number of typical bimolecular reactions only a minute fraction of the total number of collisions is effective in producing chemical change. The next step is to calculate from the probability lawwhat excess of energy the reactive molecules must be supposed to contain in order that it may be possessed only by this minute fraction of the total number of molecules. The excess of energy thus postulated is taken as the heat of activation of the bimolecular reaction. The data for the decomposition of hydrogen iodide provide a coincidence between the values calculated in this way and those deduced from Arrhenius's formula, which can only be accidental, since it is obviously far more exact than the experimental methods on which it is based. In this case the two values for the energy of activation are 43,900 and 44,000 cal., and the calculated velocity coefficient, 3-5 x 10-7 at 556° abs., is therefore practically identical with the observed coefficient, 3-52 x 10-7. A more typical case is that of the union of hydrogen and iodine, where the calculated velocity constant at 7000 is 0-14, whilst the experimental value is 0-064. This is claimed as " a very good agreement " in view of the fact that, since the two methods of deducing the energy of activation are entirely independent, the calculated velocity coefficient might very well be 10,000 times larger or smaller than the experimental value if the theory now put forward were incorrect.The method described above is particularly applicable to the study of bimolecular actions, which obviously depend in the first instance upon collisions taking place between appropriate pairs of molecules. In several of these cases it has been established clearly that the majority of the collisions are ineffective and result only in the rebound of unchanged molecules from one another; moreover, a quantitative interpretation of the phenomena can be given by supposing that the effective collisions are those which take place between molecules possessing a high energy content. The general reader may, however, be surprised to learn that when two atoms of bromine meet, the collision is ineffective in 999 cases out of 1000. It is difficult to admit that the two free atoms are insufficiently energised to combine, although this conclusion is not completely excluded; but the quantum theory allows us to suppose that in many cases the fundamental difficulty is to get rid of the energy which the atoms already possess, and it is clear that a molecule from which this energy had not yet been dissipated would be liable to break up again on the slightest provocation. The study of unimolecular reactions is much more difficult, since, if only a single molecule is really involved in the change, there is at first sight no obvious reason why the change should depend on collisions at all. It is not surprising, therefore, that there has been an energetic controversy proceeding for several years as to the mechanism of the action. Mr. Hinshelwood defines a unimolecular action as one in which the proportion of molecules undergoing change in a given time is independent of the pressure. Perrin has assumed that this law still holds good at infinite dilution, and that isolated molecules in interstellar space would have the same average life as in a closed vessel. Since this life depends on the temperature, but by hypothesis is independent of collisions with other molecules, as well as of the unknown velocity of the molecules in absolute space, Perrin and Lewis have postulated that the chemical change is due to radiation, and that its velocity is dependent on the 'radiationdensity' in the space which contains the gas. This hypothesis leads to such wildly impossible conclusions (as, for example, that an aqueous solution of a sugar should be hydrolysed with explosive velocity when exposed to the dazzling light of a tallow candle) that its survival in any form is a thing to be marvelled at. In order to avoid these grotesque conclusions, Lindemann has recently put forward an alternative theory, in which collisions play an essential part, and give rise to a definite proportion of activated molecules. The velocity of reaction must then fall off at extreme dilution, but calculation has shown, in the particular case of nitrogen peroxide (see below), that even when the pressure is reduced to 0.01 mm., the number of collisions is still far greater than the minimum number required to activate the molecules which undergo chemical change under these conditions; it is therefore impossible to make a direct test of the two alternative views at present. Mr. Hinshelwood has, however, recently described two thermal decompositions, taking place at much higher temperatures, in which a 'unimolecular' action is retarded on reducing the pressure, in accordance with Lindemann's postulates.Most of the work on unimolecular actions has been built upon imaginary cases. Thus, when Perrin and Lewis put forward their explanation of these actions, no single case was known which has survived later criticism, since all the examples that were then cited have been proved to take place at the surface of the containing vessel and not in the interior of the gas. After much searching, the solitary case of the decomposition of nitrogen pentoxide N 6-2N02 + 0has emerged, as being independent of the area of the surface of the vessel, and of the pressure of the gas down to 0-01 mm.; and Mr. Hinsheiwood himself has recently added to this exiguous list the thermal decomposition of acetone (CH3)2CO -CO + 2CH3 (?), and of the isomeric propionaldehyde; but these are queer reactions which cannot yet be represented by chemical equations, since the nature of the products is unknown, although they are obviously complex.In all these discussions the eminent president of the Chemical Society stands in the background in the unpleasant role of the spectre at the feast, since, if it be true that chemical change in simple systems generally (and perhaps always) depends upon the presence of moisture, what are we to think of speculations in which so essential a factor is ignored ? The quantities of moisture that are involved are now becoming known in certain cases, and they correspond very well with those required to produce a unimolecular film on the surface of the containing vessels. Norrish has therefore put forward the bold but fascinating hypothesis that, in the particular case of hydrogen and chlorine, the formation of a water-film on the surface of the vessel is a necessary precedent to the occurrence of chemical change in the interior of the gas. This hypothesis may not be true, but it has at least the merit of assigning a plausible role to the water in changes in which it plays a vital part, as well as to the various agents, such as ammonia, by which its action may be inhibited. In the cases now under consideration, it is claimed that " the observed rates of reaction are constant and reproducible, whether the gases have been dried carefully or not," and that " in no homogeneous reaction which proceeds with measurable and reproducible velocity has the inhibition by drying been demonstrated " (p. 103); but the outside observer, remembering the difficulties that have been experienced in the past by those who have tried merely to repeat the published work of H. B. Baker, will probably remain unconvinced by statements of this kind, until Baker himself has announced that he has tried to arrest these reactions and failed. Termolecular reactions are almost as rare as genuinely unimolecular reactions, since many of those which are represented conventionally as an interaction of three molecules, either proceed in two successive stages or take place at the surface instead of in the interior of the interacting gases. Up to the present three such cases have survived criticism, namely: 2NO + C12 = 2NOCI, 2NO + Br2 = 2NOBr, 2NO+02 = N204-The most remarkable feature of the last action is that it has a negative temperature coefficient, the interaction at 662° abs. being three times slower than at 273° abs. This is accounted for by the fact that " owing to the increasing molecular speeds there is less and less chance, at great temperatures, that two molecules shall still be within range of each other when a third one approaches. It is to be noted that the velocity of reaction falls off only very slowly, so that the diminishing frequency can account for the retrogression without undue strain " (p. 111). About one-third of the book is occupied with a description of heterogeneous reactions, but these are less uniquely the province of the author, and it will therefore suffice to say that all the main problems of the effects of adsorption, of molecular orientation, and of the texture of the catalytically active surface are discussed in a clear and satisfactory manner. In conclusion, it should be added that whilst the whole book has a definite mathematical basis, it can be read with profit by those whose ignorance of mathematics, or lack of interest in the details of mathematical processes, compel them to practice the gentle art of skipping. The book has, in fact, been written by a chemist for the benefit of other chemists, and the author's mathematical deductions are treated throughout as a means to an end and not as a final goa

ISSN:0028-0836    

DOI:10.1038/119771a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

T HE continuity of race of the present fauna of 1 the earth is due to many different factors. In the case of what we call the higher animalsslow-breeding, exposed to the attack of many sorts of enemies, in some cases subsisting on many forms of prey-accurate choice of reaction in each of a multitude of different circumstances has been, and is, a prime factor in the maintenance of race. Even where the choice of reaction may be limited, as between attack, flight, and no action at all, the determination of choice may be complicated; for the numbers of objects to which the choice is to be applied may be almost infinite.While the primary reactions (such as those mentioned above) may be classified with comparative simplicity, each individual reaction has to be modified in countless ways in accord with the variety of the object. Such ways may be briefly indicated by the expressions 'mode of attack' and 'direction of flight.' In man, the biological value of team-work has been given effect to by a great development of the mechanism of spokenspeech and heard-speech; and man probably alone of all animals is able to convey to a comrade an accurate description of the objects and changes which he observes in his immediate or distant surroundings. His behaviour, both as an individual and as a member of a team, depends, as do the reactions of other animals, upon the distinguishing of differences in the surrounding environment. Sir John Herbert Parsons compresses into scarcely 250 pages a wealth of information with regard to the perception of phenomena. To him, as to Lloyd Morgan, the progress of evolution from the more simple to the more complex is accompanied at various points by the 'creation' of new developments. It is a creed of emergent evolution, which he uses as a scientific method. In its light, the property of water is an emergent which could not have been foretold from the properties of the hydrogen and oxygen which combine to form it. There are many levels of emergence, and many sub-levels, within the main line. 'Effective consciousness '-that which enables the animal to guide its actions in the light of previous experience and to exercise choice-is one such emergent.Consciousness involves a subject and an object. The object is a sensory presentation. The sensory presentation is brought about by stimulation of receptor end-organs, and the conscious subject is aware of this stimulation. The author supposes that the simplest form of consciousness is a mere sentiency-an awareness tinged with affective tone, with a minimum of cognition, and possessing a primitive meaning, and that the subject responds with an appropriate motor reaction-" consciousness on the reflex plane." By further differentiation and integration ' awareness ' leads to 'interest' 'affective tone' emerges in 'emotion '-" consciousness on the plane of instinct." Yet further differentiations and integrations by means of memory and association give the emergence of higher ideation and conceptual consciousness" consciousness on the plane of intelligence." At every level the object of a sensory presentation has to pass through the entry enforced by the receptor organ, and differentiation of receptorsand of the whole receptor mechanism-plays a chief part in analysing the properties of the object. A consideration of data from many sources-general morphology, animal psychology, morphology of the peripheral and central nervous systems, the physiology of reflex phenomena, and observation in man-leads the author to maintain the following thesis: Primitive sentiency is essentially tactile. At higher levels response to radiations emerges and specific receptor organs of many varieties evolve. Parallel with this evolution there is an evolution in the complexity of the central nervous systemwith the development and dominance of the segments at the anterior end of the axially arranged animal, and the elaboration there of central ganglia for the distance receptors so clearly emphasised by Sir Charles Sherrington. An evolution in perception and in consciousness parallels these morphological evolutions. On the physiological side, reflex action emerges from less differentiated response; and it is inferred that the afferent impulse arouses a vague sentience analysable into two parts-into the germ of affective state and into the germ of cognitive state. The instinctive plane is an emergent from the reflex plane. There is a concomitant complexity of conscious experience, an integration without complete synthesis. Before the instinctive act occurs there is an unfocussed affective state-' coena-sthesis '-which acts as a background, and is derived from all the receptors then in activity. Upon this background emotion impinges " like a splash of vivid colour." The more discriminative reactions of the higher vertebrates are emergent from this instinctive level.In consonance with Sir Charles Sherrington's use of the term 'receptor,' the author suggests ' reception ' and ' recept ' for the act of sensing and the object sensed. Perception consists for him in the integration of recepts. Differentiation, segregation, and integration result in the emergence of a perception, which is not a mere summation of sensations. The latter " have been integrated into patterns, in which the whole is greater than the sum of its parts; something new has emerged in consciousness." The recept is more differentiated the higher we go in the scale of evolution and concomitantly with the differentiation of receptors. At the primitive level it is dyscritichaving little differentiation and little discrimination. The constellation of recepts there merely gives a change in potential in the primitive stream of consciousness. The affective tone becomes morepleasant or more unpleasant, and the motor response is correspondingly a mass reaction. In a higher level of evolution, the epicritic stage, differentiation of recepts is made possible by differentiation of receptor mechanisms The recepts form a perceptual pattern of such' a differentiation that the diverse sensations are discriminated. Awareness is focussed upon the features of the pattern and becomes attention. At still higher levels, the syncritic stage, epicritic phenomena are integrated by the cortex cerebri; attention becomes interest and ' meaning ' emerges in the perceptual pattern. The primitive dyscritic mass reaction becomes correspondingly differentiated. The perceptual pattern, at first " a buzzing, blooming confusion " accompanied by an awareness, becomes differentiated as the scale is ascended; its higher development is due to a double process on one hand of differentiation and reintegration, on the other hand of sensitisation from higher levels which have evolved contemporaneously. In the higher stages the perceptual pattern comes more under the control of higher nervous centres. One or other modality of sensation becomes prepotent, the prepotent modalities being those of the distance receptors-smell, sight, hearing. But throughout there persists a dual mechanism in sensation, the dyscritic and the epicritic both persisting. Such a brief account of the author's ' background' can give no indication of the wealth of vivid evidence from many fields which it serves, or of the facility of his presentation. Excellent and valuable accounts are given of the comparative anatomy of the central nervous system, of cutaneous sensation, of the dyscritic motor response, posture and attitude, of perception of space and of perception of movement. But the book will be valued not least for the author's description, in the chapters on vision, of the distance receptor which he has made his own more particular field; for, as Sir Herbert Parsons says, vision is the preponderant modality in man, and has undergone in him the greatest differentiation.

ISSN:0028-0836    

DOI:10.1038/119773a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

A BRIEF but very interesting account of the A Bronze Age cultures of the Minussinsk area, and a review of the literature on the subject, is given in the work under notice; the author has also some rather revolutionary ideas to put forward. The region is one of peculiar interest, lying as it does far up the Yenisei valley and forming an island of steppe country cut off on three sides from intercourse with the rest of the prehistoric world, for to the south lie mountains and to the east and west were formerly forest lands. To the north, however, lay a natural east west passage way formed by the more or less connecting river systems of the Obi, Ket and Angara leading to Lake Baikal. The author stresses the contention that the early Bronze cultures of the district owe nothing directly to the west, i.e. to the Bronze cultures of the Ural mountains, though both may originally have had a common source. He believes that it was not until very late that any western connexion was established, and that similarities in the two cultures can then be explained by a parallel reception of Scythian influences. To the reader it is not quite clear from exactly where the author would like to derive the people whose industries he is describing. South, east, and west being blocked, as already described, they must have arrived as a back wash from the north, following the Yenisei southwards, but where they originally came from seems uncertain. Having settled, however, in this blind-alley district, it would appear that a slow development took place which was at first little influenced from outside owing to the peculiar geographical position of the area. A very late chronology is adopted; in fact round about 600 B.C. is given as a mean date for the full Bronze culture here.The chapters devoted to a description of the finds themselves are very interesting, and the illustrations quite adequate. An earlier and a later type of grave (called respectively ' corner stone ' and 'collective ' graves) are described, from which it would appear that an outside influence must have penetrated the region, but not a new race, as many of the old characteristics continue in the new graves. Finds unconnected with burials are also discussed. Of these the K-rasnojarsk celt is the most important, and its distribution problems are very complex. Several chapters are devoted to typological study and decoration motifs. The only regret one has when putting this book down is that the author has kept so rigidly to the period under review. One would like to have known what he thinks existed before the first culture with which he is concerned. Again, there are rock engravings not so far off from his region, some of which are probably of late date, but othersmay be very early indeed. A brief mention of them would have been welcome.The book is very interesting, deals with a littleknown but important area, and the author is to be congratulated upon having tackled his subject in a systematic and scientific manner.

ISSN:0028-0836    

DOI:10.1038/119775a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE career of Sir Joseph Whitworth, one of the greatest engineers of his time, is especially interesting, since he was the first man to grapple successfully with the problem of obtaining precision of workmanship and the standardisation of screw threads. It is difficult to realise now that, when he began work rather more than one hundred years ago, it was exceptional to find men able to make parts of machines to an accuracy of one thirty-second of an inch. His epoch-making discovery of a method of making a true plane by a process of scraping and comparing three plates together made it at once possible for engineers to produce work of the utmost precision. This was followed by the manufacture of very accurate screws and the construction of workshop machines to measure lengths to one ten-thousandth of an inch. Indeed, Whitworth was successful in constructing a machine capable of detecting a difference of one millionth of an inch. His surface plates, gauges, and measuring machines soon became established in all engineering workshops and revolutionised their practice, while his machine tools were admittedly unsurpassed.Although others had attempted the standardisation of screw threads, no one had been able to effect this until Whitworth took the matter in hand and, by adopting the best features of existing systems, brought about an agreement which has received world-wide recognition. In his later years Whitworth was equally successful in improving the manufacture of rifles, large calibre guns, and fluid-compressed steel. Whitworth's practical mind also realised the necessity to the engineering industry of a continuous supply of young engineers who, in addition to workshop experience, were thoroughly conversant with applied science. Having acquired a large fortune in his manufacturing career, he was able to put his ideas into practice by setting aside £3000 a year for scholarships, and at his death £100,000 was handed over to the State to carry on the scheme associated with his name.The Whitworth Book is the " Who's Who " of about one thousand Whitworth Scholars appointed under this munificent scheme: Its pages show how vast an effect this scheme has had on modern engineering in every direction of activity. Probably no engineering work of this great man has been more successful than this final one. The Whitworth Society, and especially the honorary editor, are to be congratulated on having produced a very interesting work of permanent valu

ISSN:0028-0836    

DOI:10.1038/119776a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

AN addition of a novel character to the museums of Great Britain has been made recently in the form of one devoted entirely to fire-making appliances. Fire making is of vital human interest, and here we see the many methods that have been used in past ages and in different climes. Messrs. Bryant and May's collection at their Fairfield Works, Bow, in the main is that formed by Mr. Edward Bidwell during a period of half a century. Perhaps this should have become a national possession, but within the last year it passed into the keeping of the firm, who have housed it admirably. Considerable additions have been made, and it includes every known method of fire making. It is, indeed, so comprehensive that it is difficult to conceive that it can ever be rivalled. The objects are classified under tinder; wood-friction methods; flint-andpyrites methods; flint-and-steel methods; quartzite-and-iron methods; optical methods; compression methods; chemical methods; and finally the friction match. Of the exhibits, about half represent the flint-and-steel and friction-match methods. The museum is not open to the public indiscriminately, but is accessible to the student, societies, etc., without charge, during week-day afternoons or Saturday mornings, on application to the firm.

ISSN:0028-0836    

DOI:10.1038/119777b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

MAY I place on record what is, I think, the most direct evidence that the modified scattered radiation is due to the super-position of unmodified scattered radiations? When using a certain primary X-radiation, the scattered radiation from air was found to be totally unmodified radiation,i.e. a radiation with accurately the same absorbability as the primary radiation exciting it. The radiation scattered from paper or paraffin-wax was very definitely a modified scattered radiation, or contained a modified radiation,i.e. differed considerably in absorbability from the primary radiation. Also these two radiations scattered from paper and from paraffin-wax were equally modified—within a small possible error.Such results have frequently been obtained in this laboratory. As previously recorded, we have even obtained modified scattered radiation from thick sheets of scattering material, when the radiation from thin sheets was an unmodified radiation as tested by absorption measurements. In our recent experiments, however, we made a systematic examination of the radiation scattered from various thicknesses of scattering substance. It was found that with a certain primary radiation, when the sheet of paper or paraffin-wax was made gradually thinner, the difference between the primary and scattered radiations became smaller, and ultimately almost vanished, indicating very definitely a vanishing difference for an infinitely thin layer of scattering material.The possibility of this effect being due in some way to a mere variation of the intensity of ionisation is quite ruled out of consideration by the facts that (1) A large variation of output of the Coolidge tube was entirely without influence on the measured difference between primary and secondary radiations, and that(2) Equal degrees of modification of the rays scattered from paper and from paraffin-wax were produced by scattered radiations of quite different intensity. Thus the slab of paraffin-wax used as scattering substance had to be seven or eight times as massive as the slab of paper in order to produce an equal degree of modification in the scattered radiation as measured by absorbability. Under such corresponding conditions, the intensity of the scattered radiation from paraffin was, roughly, seven times the intensity from the paper. Plotting the change of absorbability on scattering against mass per unit area of the scattering sheet, we obtained curves of form precisely like the familiar ionisation-pressure curves showing saturation current. In our experiments what was shown was a saturation amount of modification by scattering from thicker layers of scattering material. The maximum amount of modification was shown much earlier for a paper than for a paraffin-wax scatterer, but the two measures of modification were finally equal. Other experiments on this phenomenon-for it of course raises many questions-will be described elsewhere.It should, however, be added that all X-radiations are not equally sensitive to a change in the amount of scattering substance. The scattering radiation was evidently near the critical condition for a change of its level of activity such as we have described in papers on the J-phenomenon. It afterwards settled down to a state in which thick sheets, thin sheets, and even air itself all produced a scattered radiation showing the full amount of modification such as had previously only been given by thick sheets. It is, of course, possible-indeed I think probable-that it was thennecessary only to experiment upon much thinner layers still, in order to obtain the vanishing amount of modification by scattering. This, however, was beyond the range of experiment. What we have shown is that by experimenting on a suitable radiation, a perfectly regular development of the modified scattered radiation can be traced to the superposition of unmodified radiation from thin layers. This further illustrates what we have previously described as the coherence of superposed X-radiations. Neither quanta nor wave-trains within narrow limits of wave-length can be considered independent in their action; it is the whole stream of radiation which is effectiv

ISSN:0028-0836    

DOI:10.1038/119778b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

I SHOULD like, first of all, to express my regret that up to now Dr. Campbell's most interesting papers have escaped my notice. The expressions which I used, and to which Dr. Campbell takes exception, would certainly have been more precise had I taken account of Dr. Campbell's work.As for Dr. Campbell's idea, I should like in the first place to point out that the matter has been considerably advanced by two papers by Dr. Dirac (P. A. M. Dirac, Proc. Roy. Soc., London) and by me (P. Jordan, Z. fiir Phys., 40, 809; 1927) on the foundations of quantum mechanics, and by Dr. Heisenberg's "'tber den anschaulichen Inhalt der Quantenmechanik," which is based upon them (W. Heisenberg, Z. flir Phys., in press). These investigations corroborate Dr. Campbell's opinion in certain respects; on the other band, they indicate certain limitations. Heisenberg has explained how the Cartesian coordinates, e.g. of an electron in hydrogen atoms, can be regarded as exactly measurable; and correspondingly one must consider the 'fourth co-ordinate' q4=ict as exactly definable and measurable. The difficulties of a measurement of t which are brought out by Dr. Campbell arise in the measurement of every physical quantity in an atom (e.g. energy). How and to what extent these difficulties can be overcome has been considered in detail by Heisenberg. In this respect, therefore, the quantum mechanical conceptions differ from those of Dr. Campbell. In a certain respect Dr. Campbell's views are, however, confirmed by the quantum mechanics: for if the atom has specified quantum numbers, the time (and the co-ordinates) are statistically, and only statistically, defined. For the characteristic feature of the quantum mechanics is that one cannot specify simultaneously all of the 2f constants of integration of the classical dynamised system, and, in particular, that one cannot specify both a co-ordinate and its conjugate momentum. Similarly, one may specify the energies of the initial and final states of a quantum jump; then the time of the jump is indeterminate. But one can equally well specify the time of the jump, and leave unspecified the initial and final states; and within certain limits of accuracy one can specify both the initial and final states and the time.Undoubtedly this discussion is too short and too inaccurate to elucidate the point completely. I should like, therefore, to refer Dr. Campbell again to Heisenberg's paper, in which these questions are treated in detail.

ISSN:0028-0836    

DOI:10.1038/119779b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT is rather hesitatingly I venture to discuss one or two remarks by Prof. Hale in his interesting contribution entitled “The Fields of Force in the Atmosphere of the Sun,” in NATURE of May 14, p. 708.The instances in which I have observed, with perfect ease, intensely black (and bright) hydrogen flocculi, often of stupendous magnitude, suddenly develop near active spots, and even where no conspicuous spots were visible at all at the moment, can be counted by the hundred in my observational notes. I have frequently taken occasion to describe such observations in scientific journals, as well as alluded to them in my annual report to the Monthly Notices of the Royal Astronomical Society, which circumstance I wish to mention particularly, because Prof. Hale seems to attribute this kind of observations exclusively to the capabilities of the spectrohelioscope, whereas a good solar grating spectroscope has shown me practically all the phenomena he describes, on many occasions. Had I at my station the superior apparatus of Mt. Wilson, or Pasadena, at disposal, and above all the incomparably more numerous and favourable observing opportunities afforded by Californian skies, I should of course be able not only vastly to increase the number of my observations, but also to enjoy better access to the finer detail only seen here when the air conditions are best. I have also pointed out the drawback of the second slit of the spectroheliograph, which obscures deflexion effects beyond the amount permitted by the width of the second slit, such effects showing perfectly satisfactory with the single slit solar spectroscope. If enhanced seeing is desired, the introduction of a second adjustable, and laterally movable, slit in the focal plane of the ocular of the view-telescope helps to exclude unwanted light from the field of view. Of course, if the second slit is set too narrow, the same difficulty just mentioned in connexion with the second slit of the spectroheliograph is introduced, wherefore in the case of displacement observations, the second slit in the ocular is opened out to the maximum amount of displacement seen through the first slit. Good vision of such evolutions is further enhanced by the use of an eye-cup attached to the ocular of the view telescope.In spite of the many observations (also shared by myself), which have caused other writers to state that the dark flocculus was sucked through the spot cavity into the interior of the sun, this contention cannot be correct for purely physical and mechanical reasons attending spot evolution. The flocculus may be seen drawn towards the spot vortex, from above and from aside the latter, but on nearing the general upper levels of the spot-umbra, this indrawing action becomes arrested and the gases of the flocculus start to partake of the radial outflow of the gases coming up the spot-cavity from the interior. Where the flocculus encounters these, it becomes heated up temporarily into brightness before being scattered sideways into the penumbral regions. On May 7, 1927. at 1.45 Greenwich Summer Time, I had the good fortune to witness an exceptionally brilliant eruptive prominence shoot out near Position Angle 850. The display was for a few minutes of such intensity that the whole length of the spectrum showed indication of being traversed by a ribbon of continuous light. Leaving the slit tangential to the same Position Angle, but using the direct reflecting position of the grating, I had no difficulty in discerning the clear-cut, pale-white form of this prominence. Its brilliance in the first order of the spectrum induced a reasonable expectation of this direct view, and I feel positive that such a prominence would be readily visible at sunrise, or sunset, with the sun's limb just registering with the hori

ISSN:0028-0836    

DOI:10.1038/119780a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IT has often been stated, and is very generally believed, that no deposits analogous to the Arctic peats of Scotland occur in Ireland. The proximity of the two countries is so great, however, that climatic conditions which affected Scotland must have affected at least the northern portions of Ireland in a similar degree, and it is not surprising, therefore, that an Irish Arctic peat, or something approaching one, has at last been discovered. This peat bed in question is situated on the boundary between the counties Dublin and Wicklow, on the eastern slopes of the Dublin mountains. Locally the place is known as Ballybetagh and Mulligan's Bogs, the former lying in Dublin, the latter in Wicklow. Both bogs have long been famous for the vast quantity of remains of the so-called Irish elk, which has been found beneath them.The site of the bogs is an oval depression about half a mile long (north to south) by a quarter of a mile in width, and was occupied in late glacial and early postglacial times by a (?) shallow lake, now entirely filled up by deposits of various kinds. The first post-glacial stratum to be laid down in the lake was a fine bluishgrey clay, sometimes containing chips of stone or gravelly layers, derived by subaerial denudation from the moraines surrounding the site. Resting on this clay, and often bedded into it, lie the scattered bones of the great deer; while in turn these are covered by a flaky peat-locally known as " elk deposit "-which, besides numerous seeds, roots, etc., contains many leaves of Salix herbacea. At present my claim that this is an Arctic peat rests solely on the evidence afforded by this willow, though I have just heard from Dr. G. Erdtman, of Stockholm, that a hurried and superficial examination of a sample of the peat from Mulligan's Bog has convinced him that it " is sub-Arctic, if not Arctic." I have to thank Dr. Henry Stokes, of this city, for permission to examine numerous sections at Mulligan's Bog in August 1926, when he was digging for remains of the Irish elk. I have also to thank Miss M. C. Knowles, of the National Herbarium, for confirming my identification of the leaves of Salix herbacea. I may add that the leaves from Mulligan's Bog differ greatly from those of the same willow now growing in the Wicklow Mountains at altitudes of from 2000 ft. to 3000 ft., and resemble the leaves of prostrate specimens of the plant in the National Herbarium from Arctic Europe and Labrador. The present lowest limit of Salix herbacea in Wicklow is a little more than 2000 feet altitude, thus suggesting a considerable lowering of the snow-line during the period in which the peat was deposited, Mulligan's Bog being only about 750 feet above present sealevel.There is at present no proof, but I suggest that the Irish elk may have lived during a comparatively mild period, and that the peat containing the leaves of Salix herbacea may be contemporaneous with one of the re-advances of the ice-when the Scottish ice sheet was forming its terminal moraines along the north-east coasts of Ireland, on the Isle of Man, Cumberland, and in south-west Scotland. For evidence connected with these moraines see " The Re-advance, marginal kame-moraine of the South of Scotland, and some later stages of retreat," by Dr. J. K. Charlesworth (Trans. Roy. Soc. Edin., 1926), and also A. R. Dwerryhouse in Quar. Jour. Geol. Soc., 79, 352; 1923.

ISSN:0028-0836    

DOI:10.1038/119781b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature