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temperature regulators and air conditioning. The sections dealing with the amount of heat required for warming and with the heat given off from radiating surfaces are of special interest. It must, of course, be understood that the efficient warming of a large building is a matter that is not susceptible of absolute mathematical calculation, and a great deal of the measure of success attained lies in the manner in which the warming and ventilating appliances are handled by those in charge. The volume before us has proved in the past to be a useful guide to architects and others responsible for providing the arrangements, and with the information which it now contains will no doubt prove equally useful in the future. Structural Steel Drafting and Elementary Design.

By C. D. Conklin, Jr. Pp. vii+ 154. (New York J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1915.) Price 10s. 6d. net. THE author's object in compiling this book has been to provide a treatise dealing adequately with the preparation of shop detail drawings of structural steel work. Such a book is required no less in Great Britain than in the United States. In both countries there are several very good books dealing with the design of structural steel work. Some of these contain excellent expositions of the more theoretical work, but they do not meet the requirements of the practical draughtsman, and speaking generally, leave the reader with a very small knowledge of structural details. The book before us gives a clear and minute description of the methods adopted in some leading American drawing offices, and includes designs of riveted connections, beams and columns, steel roofs, a deck plate girder railway bridge, a through girder bridge, etc. Fullydimensioned working drawings are given as well as the simpler calculations required in the design. The book is thus suitable for use in technical colleges, and provides a fairly complete course in structural drawing office practice. With a few minor modifications, which the teacher can easily supply, the book can be brought into line. with British practice and nomenclature, and ought to be of service to students of structural steel work in this country. Calculus Made Easy.

Edition. Pp. x+265.

Second By F. R. S. (London: Macmillan and Co., Ltd., 1914.) Price 2s. net. THE author of this book has added many worked examples and exercises to those in his first edition; otherwise the book is but little altered and we have not much to add to the remarks we made

five years ago. The motto is, "What one fool can do, another can." Perhaps there may still be too many encouraging remarks of a jokesome nature and too many expressions of disdain for the stupidity of the usual methods of teaching, but the title of the book is justified. The author does show that the most fundamental operations of the calculus are easy to understand and may be performed by beginners with success, that is, without vague notions of being wrong. J. P.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Surface Tension and Ferment Action.

MESSRS. BEARD AND CRAMER, in a paper under the above title published in the Proceedings of the Royal Society issued on June 1, describe experiments made with invertase with the object of determining "whether the action of a ferment on a substrate is affected by surface tension." They answer this question in the affirmative and draw far-reaching conclusions.

The method they use, however, is open to very serious criticism; we think that there is little doubt that the phenomena they describe are due entirely to the effect of alkali and not to change of surface tension. They have compared the activity of invertase towards cane-sugar in tubes filled either with glass wool or with capillary glass tubes or with glass beads with that of a control in an ordinary test-tube. Retardation of action was observed in all such cases.

All who have experience in working with saccharoclastic enzymes are well aware how extraordinarily sensitive these are to the influence of the minutest trace of alkali. This applies to the enzyme invertase in particular. In a paper published in the Proceedings of the Royal Society so far back as 1907 (Series "B," p. 362) we pointed out that unless hard glass vessels were used, it was impossible to obtain consistent results; in fact, it is not only necessary to carry out the action in hard glass vessels but it is essential also to use storage bottles and measuring pipettes of similar hard glass: even then the results are apt to be irregular.

The work done by Sörensen in co-ordinating enzyme activity with the degree of alkalinity or acidity of the medium is too well known to need description; his experience with invertase shows clearly how much the activity of the enzyme is influenced by the minutest trace of alkali. We look in vain in Messrs. Beard and Cramer's paper for any reference to the possible influence of alkali derived from the soft glass they used as a cause of retardation; it would appear that they have entirely overlooked this factor. So long as no definite evidence is brought forward to show, that the retardation change they observed is not due to the action of alkali, it is unnecessary to attribute it to the influence of surface tension.

E. F. ARMSTRONG. H. E. ARMSTRONG.

Training for Scientific Research.

IN connection with our position in regard to chemical industry, the present seems to be a suitable time' for a careful discussion of what is doubtless not a new suggestion. It is a sufficiently obvious fact that the German chemical trades-especially those that most require highly-trained chemists--prosper in very much greater measure than our own, and, by general consent, the reason for this appears to be that the Germans appreciate the value of research more than we do. How then is a better appreciation of research to be fostered in this country? Various proposals to this end are being made; closer relationship between technical and theoretical chemistry, whatever that may mean; the establishment of an industrial council; the founding of scholarships, etc., all, doubtless, good things in their way, things, however, which have been

tried already to some extent, but unfortunately without sufficient success to justify an expectation. of their being able completely to accomplish the desired change.

In considering this question we ought, it appears to me, to search for some distinct difference between our educational practice and that of Germany, some difference great enough to be likely to have an important effect. Such is indeed easy to find, for there exists a difference so great that it might quite readily lead to very important results, and one which, probably because of its obviousness, is generally ignored. This far-reaching difference is simply that in Germany research work is absolutely indispensable for the ordinary degree (by "ordinary" I mean that ordinarily taken by students), and it is at least a very reasonable contention that the moment research work becomes essential for our ordinary degree (B.Sc.), with, naturally, any necessary lengthening of the course, so soon shall we have taken the step which will, not to-morrow, but in ten or fifteen or twenty years' time, perhaps place us on something like an equality with Germany in respect to the point at issue. Two most important results might be expected to follow the introduction of compulsory research into the B.Sc. degree: (1) There would be provided throughout the country a considerable body of young chemists with some experience, say one year, at least, of research work. There is such a thing as a general method in research, and after even only one year's training in it the young chemist would be able to attack, with very much greater confidence than at present, many of the problems which arise in industrial practice, for in research work, emphatically, it is the first step that counts for most, and this first step being a thing that can be taught, it is the duty of the universities to teach it. (2) Sons of manufacturers who go to the university and take a science degree would of necessity carry out some original investigation, and from this particular class-composed of men who, for the most part, are possessed of some means and leisure-there would be likely to emerge a number of really capable chemists, who might indulge in the higher degree of D.Sc., men likely to carry their chemistry intelligently into their businesses. But even in those least interested there would necessarily be acquired some idea of what research means, some notion of how it might be applied to their own particular requirements, and it is probable that in a comparatively short time, say twenty years, the lack of appreciation of research work which is now attributed to the manufacturer would have wholly or largely disappeared.

In fact, the introduction of research into the ordinary degree would be likely to act in several ways. First upon the student, secondly upon the manufacturer, and thirdly upon theoretical chemistry by the achievement of the excellent educational principle, that the science would be the richer in some fact or in some theory for every graduate who had devoted himself to it. Fourthly, it would react upon the teachers.

Although this is, essentially, an exceedingly simple reform, there would doubtless be great difficulties in carrying it out; it would probably be urged that M.Sc. degrees have been instituted with this especial object, but that would be to misunderstand the present suggestion, the essence of which is that there shall be no degree at all, or anything resembling a degree, which does not require research work. At the present time, however, when traditional prejudices of all sorts are going by the board, it would probably be easy for the teachers to bring sufficient pressure to bear upon Parliament, or conversely, for Parliament or a resolute Government to

bring sufficient pressure to bear on the teachers, to secure the immediate accomplishment of this desirable improvement.

It must, however, be sorrowfully admitted that such a change is not likely to make any particular financial difference to the young chemist, but in all probability it would give him a better opportunity for advancement once he had established himself in a technical post, and there is little doubt that the advantage to the country would be very great. T. S. PATTERSON. University of Glasgow (Organic Chemistry Department), June 8.

Galileo and the Principle of Similitude.

WHEN I said in NATURE (April 22) that Herbert Spencer was the first to apply the principle of similitude to dynamical problems in biology, I spoke in haste. I might have remembered that Borelli had shown, by help of this principle, that a man would never be able to fly by his own muscular power, and why (for instance) small animals are more active and leap higher than big ones. But I was quite ignorant of the fact that Galileo had treated the whole subject on the broadest lines and with the utmost clearness. His discussion will be found in the "Dialogues concerning Two New Sciences," admirably translated by Prof. Henry Crew and Alfonso de Salvio (New York: The Macmillan Co.; London: Macmillan and Co., Ltd., 1914). So numerous and interesting are the subjects dealt with in this wonderful book that the writer of a long and laudatory notice in NATURE (December 24, 1914) had not time or space to mention that the prin ciple of similitude and the subject of animal mechanics are alluded to therein. The following extract (op. cit.. p. 130) is but a small part of what Galileo has to say upon the principle of similitude :

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Salviati: From what has already been demonstrated, you can plainly see the impossibility of increasing the size of structures vast dimensions either in art or in nature; likewise. the impossibility of building ships, palaces, or temples of enormous size in such a way that their oars, yards, beams, iron-bolts, and, in short, all their other parts will hold together; nor can nature produce trees of extraordinary size, because the branches would break down under their own weight; so also it would be impossible to build up the bony structures of men. horses, or other animals so as to hold together and perform their normal functions if these animals were to be increased enormously in height, for this increase in height can be accomplished only by employing a material which is harder and stronger than usual, or by enlarging the size of the bones, thus changing their shape until the form and appearance of the animals suggest a monstrosity. To illustrate briefly, I have sketched a bone the natural length of which has been increased three times and the thickness of which has been multiplied until, for a correspondingly large animal, it would perform the same function which the small bone performs for its small animal. From the figures here shown you can see how out of proportion the enlarged bone appears. Clearly, then, if one wishes to maintain in a great giant the same proportion of limb as that found in an ordinary man, he must either find a harder and stronger material for making the bones, or he must admit a diminution of strength in comparison with men of medium stature; for if his height be increased inordinately, he will fall and be crushed under his own weight. Whereas, if the size of a body be diminished, the strength of that body is not diminished in the same proportion; indeed, the smaller the body the greater its relative strength.

Thus a small dog could probably carry on his back two or three dogs of his own size; but I believe that a horse could not carry even one of his own size.' "Simplicio: This may be so; but I am led to doubt it on account of the enormous size reached by certain fish, such as the whale, which, I understand, is ten times as large as an elephant; yet they all support themselves.'

"Salv.: 'Your question, Simplicio, suggests another principle. . . .'"-And thereupon the two disputants go on to discuss the effect of immersion in water, of how by reason of its density (corpulenza), or, "as others would say," its heaviness (gravitá), the weight of bodies immersed in it is diminished; and how accordingly the body of the fish is rendered, so to speak, altogether devoid of weight, and is supported without any injury: though if a giant fish, or a great and heavy-laden ship, were drawn ashore, it would be apt to go all to pieces, crushed under its own mass. Galileo points out that Aristotle had an inkling of the principle in that chapter of his Mechanics" where he discusses the question, "Why a long beam is weaker than a short one "-even though the long

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beam be thick and the short one be thin. But at the beginning of his treatise Galileo makes it clear that he regards the general statement as a discovery of his own, and as one of great importance which moved him even to astonishment.

D'ARCY W. THOMPSON.

The Names of Physical Units.

A L'OCCASION de l'aimable analyse consacrée au "Recueil des Constantes physiques" (NATURE, May 13, p. 281), M. J.-A. Harker s'étonne de certaines expressions insérées dans le tableau dont je suis à moitié responsable, et qui sert de préface à tout l'ouvrage. Je dis "à moitié," car, à l'encontre de ceux qui se rapportent à des constantes proprement dites, le tableau des unités a été discuté et approuvé dans sa terminologie par la Commission tout entière; j'ai seulement proposé, la Commission a disposé.

Le terme stéradian n'a pas l'approbation de M. Harker. Evidemment, il n'est pas encore consacré par un usage international, et c'est là, peut-être, son plus gros défaut. Les physiciens français toutefois l'emploient couramment pour désigner l'angle solide découpant, sur la sphère, une superficie égale au carré du rayon, ou l'angle solide égal au quotient de l'espace entier par 4. On conviendra que l'une ou l'autre de ces expressions est encombrante, et qu'une contraction était au moins désirable.

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Stéradian est logique, puisqu'il résulte de l'association de radian (angle plan unité) et du préfixe impliquant la solidité ou l'espace à trois dimensions. J'ose donc espérer, malgré l'étonnement Harker, voir nos confrères britanniques adopter ce terme. Ce serait une aimable réciprocité à l'hospitalité donnée par les sportsmen continentaux au mot starter, grâce auquel ils évitent aujourd'hui la périphrase: Fonctionnaire chargé de donner, dans une course, le signal du départ; tout comme le titre qu'ils s'octroient abrège cette autre appellation: Gentlemen consacrant une partie de leurs loisirs aux exercices musculaires.

La question du degré carré sera résolue avec celle du stéradian. C'est bien, si je ne me trompe, au moyen de cette unité que les astronomes évaluent, entre autres, l'espace de la sphère céleste que couvre un cliché photographique.

Une autre espèce d'expressions a frappé M. Harker masse volumique, volume massique. Dans le tableau en question, ces expressions sont inscrites entre parenthèses, en subordination, pour ainsi dire,

des termes classiques mais bien peu satisfaisants : Densité absolue et volume spécifique. Si j'avais eu une entière liberté, j'aurais certainement franchi l'étape et renversé l'ordre. Quel qualificatif, en effet, laisse plus de vague à l'esprit que celui de spécifique? On dit masse spécifique quotient de la masse par un volume; volume spécifique quotient d'un volume par une masse; spécifique a, ici, les deux acceptions exactement opposées, sans compter, dans d'autres cas, une foule de sens divergents. En fait, spécifique signifie tout ce que l'on veut, et par conséquent ne signifie rien du tout. La vieille terminologie laisse encore traîner dans la physique des expressions telles que chaleur spécifique (capacité calorifique rapportée à la masse) et résistance spécifique (résistance rapportée aux dimensions) et tant d'autres, pour l'intelligence desquelles le physicien est chaque fois obligé de faire appel à sa mémoire, sans certitude d'être d'accord avec un confrère dans le sens à attribuer à une même expression.

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'Some eccentricities appear in the initial table on units; few physicists are familiar with such terms as 'volume massique' and 'masse volumique,' ' degré carré' and 'stéradian.

I expressed no opinion as to the suitability of any of the terms in question, but only pointed out that in my view they were as yet far from familiar to the average physicist.

I have taken an opportunity of testing the accuracy of this opinion by consulting six of my colleagues. Not one of these had a clear and definite idea of the meaning of all four of the terms in question.

The introduction of a new name for a unit or an alteration in nomenclature should be a matter for the most careful consideration, particularly if it is intended for general international use; more harm than good may easily be done by an injudicious choice, even if supported by a great authority.

"Stéradian," and the other terms too, may be logical, but it is unpractical to attempt to build a language simply upon logic.

Dr. Guillaume will remember that some time after the use of the term micron, with its corresponding symbol, the overworked letter μ, had been introduced into metrology, as the name for the millionth part of a metre-I believe I am correct in saying, largely through the influence of Dr. Benoit-Lord Kelvin,

probably unaware of this, proposed that the name michron be given to the millionth of a second, while he suggested that the micrometre be termed the microm.

Similarly, many years ago Sir Benjamin Brodie attempted to induce the chemists to rationalise their nomenclature by re-naming CO carbonous oxide, and taking the name carbonic oxide for CO2.

Had either of these proposals even partially materialised, it would undoubtedly have led to great confusion.

While to some extent I agree with Dr. Guillaume's remarks regarding the English use of specific," I do not think he strengthens his general case by referring to "puissance massique," which, to my mind, conveys only the haziest sort of meaning.

I might point out that, according to a view I have heard frequently expressed, the general introduction of the metric system into England has been hindered by prejudice against what is considered the unnecessary number of names of units appearing in the usual books dealing with the subject. It may be desirable to have these for rare use, but it is surely inadvisable to mention them in the school books as if they were current. Thus, for example, among measures of length, one is accustomed to think in metres, centimetres, or millimetres, and of greater lengths in kilometres. The decimetre is rarely used except in connection with the litre, and the decametre, hectometre, and myriametre practically never.

In conclusion, I think I represent the views of readers of NATURE when I say that many of them will be glad to buy the French Physical Society's useful volume, if it is only to be able to get rid from their library table of one or other of the editions of its well-known predecessor, written in the language of the Huns, which at the present moment they are unable to tolerate. J. A. HARKER.

Teddington, May 25.

University Appointments in War Time.

I VENTURE to direct attention to the advertisement for a professor of organic chemistry in the University of Liverpool. It appears to me, and I believe many share my opinion, that this is a very inopportune moment for filling a university chair when eligible men are away on active service. It may seem unfitting to criticise the internal policy of another university, but it is a matter which closely affects many who have no connection with the University of Liverpool. Professors of chemistry and others are being solicited for testimonials by candidates, and in many cases such requests cannot be granted except by doing a grave and irreparable injustice to more highly qualified men who have responded to the country's call for volunteers in the present national crisis. I trust that the University of Liverpool will in this matter follow the same course as has been pursued by the University of Birmingham in the case of the vacant chair of physics, and postpone the appointment of a professor until after the termination of the war.

PERCY F. FRANKLAND, (Dean of the Faculty of Science). The University, Birmingham, June 12.

Volunteers for Scientific Work. CIVILIANS of all grades are being enrolled as volunteer workers in our ammunition factories. Are there no Government chemical factories where persons of a certain amount of scientific training could render

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A state of war has disclosed this in detail; and demonstrated that a nation which is illprepared against industrial expansion in the modern sense, finds itself in an inferior position in times of war. For reasons which are still somewhat obscure, the British manufacturer has shown in the past a distinct preference towards those industries which develop best on lines of empiricism. Many have held that this is a defect; the present position has proved this to the hilt. manufacturers have surrounded themselves with an atmosphere which demands their whole attention in directing their ventures as they exist, manufacturing articles which depend upon a market already existing and the low selling price which always goes with such conditions. If empiricism were the only law of manufacture (as it was some fifty years ago) they would by their application outdistance all competitors.

It has been to Germany's credit that she realised the great driving force behind this system as it has been practised in the northern part of these islands, and that to turn the shield concentration in other directions was demanded, where some new factor could be introduced and the methods of empiricism were useless. British methods were not so much improved upon as superseded; scientific supervision and investigation were the beginning and end of this development; industries were built up which could not even have been started under the old régime; industrially useful products were in the scientific sense in many cases created, and then introduced into commerce. The older method of improving existing manufacture by empirical methods gave place to a new system. Thus the British manufacturer found himself face to face with the German industrialist, who had already convinced the German banks that he was working for a new era, where profits would be large and developments world-wide. To-day we have to consider a position where many of these new industries (by chance, or design) have been of the first importance in the time of war. The manufacture of large quantities of ammonium nitrate and nitric acid from synthetic ammonia (or the nitrogen of the air), has made Germany free from outside supplies of nitrates, and thus to some extent counteracted

1 "First Principles of Production. A Study of the First Principles of Production and the Relation of Science to Industry." By J. Taylor Pedcie. Pp. 231. (London: Longmans, Green, and Co., 1915.) Price 5s. net.

our command of the sea. Extensive coke-oven plants, while tending to commercial efficiency in times of peace, have given her a supply of raw material for high explosives in times of war. Her extensive liquid chlorine plant has also been turned to notorious use.

The lesson of all this is that a nation lags behind in scientific development at a cost of a possible loss of supremacy in times of war. A state of unreadiness in this direction is co-extensive with its influence and life. Industry developed on empirical lines has a certain advantage in times of peace, for it has at its command markets of great strength and deals with large outputs, but it is one-sided. It actually It actually leads into a backwater where adventure is suppressed in favour of mere attention to detail; the walls of the factory or works being the natural bounds of the manufacturer's interests; his energies confined within a few yards of buildings. In other words he is working in the proverbial rut. Industrially he is entirely

domesticated.

It would be impossible to deny that in certain directions this system has its advantages; or that many industries are undoubtedly sound under such conditions. Also that certain phases of Empire have partly directed industry into the lines we have followed, where a large output of universal application is essential. The distressing limitations of such a system have only come to be universally recognised under the stress of war.

Now the British manufacturer is called upon suddenly to turn industrialist, and to co-operate with the scientific investigator to consider our industry as a whole. The danger of such a rapid change will be seen in the persistence of command which is essential to empiricism, as seen in the attempt to control rather than co-operate. This will only represent a transition stage, serving a purpose in the course of a radical alteration in procedure.

It is for the scientific worker to see that this intermediate stage is made as short as possible; that recognition of the work of the investigator shall be complete in all directions. This can best be achieved by taking an active interest in industrial affairs. To be merely academic will not suffice, for this offers no encouragement to the manufacturer to hold out the hand of friendship. When obliged by the circumstance of the moment to seek scientific advice he has turned to those who have technical experience rather than a studied condition of brain energy directed in the display of pure science. That a severely academic attitude has reacted against the application of science to industry is certain. The effective antidote against such a condition is a greater interest in application, as apart from theory. This can be most easily achieved by a linking up with some specific industry, which method has led many a German chemist to widen his horizon and plan of research. The effect of such a change in this country would be magical.

It would react progressively both on science and industry.

The scientific worker must never forget that the business man has achieved great things for this country in the past. This is our hope for the future when he will work in partnership with the experimentalist. Such a change in attitude is an essential preliminary to a working arrangement between the interests involved. The business man will then realise that a new factor has come into his affairs. While scientific endeavour is almost entirely confined within the college walls, and recorded in the journals of learned societies, this will remain unrecognised. What is required is an is required is an active partnership between the trained investigator and those who specialise in the means of actual manufacture. The manufacturer must be convinced that certain modern industries are so bound up with experimental science that they are inseparable; that they cannot be run on the lines which were so successful in the case of the older industries.

It may even be that a thorough awakening of science is more necessary than that the business man should afford recognition. So far as chemistry is concerned, the division of those actively engaged in this science (as roughly represented by the different societies) has not altogether made for progress as a whole. Science must speak with a collective authority and with no uncertain voice. It must demonstrate by the conduct of its own affairs that it is capable of leading; that its advent into the industrial (and political) world will bring order and not chaos At this late stage of development, the English business man will only respond to a party which exhibits by action. the essential qualifications of its watchword.

Thus the passing of a certain sense of exclusiveness on the part of those who follow research is a preliminary step towards recognition by the commercial world. An advance on parallel lines is not business. Against this system we have the close association of the German method which has resulted in a solid network of endeavour.

Just so long as our advance is confined to empiricism, so long will the work of the chemist be chiefly directed towards the mere testing of material, instead of the legitimate work of developing new processes and manufacturing new materials. The war has cleared the air, and clearly points to a new path which we shall do well to follow, the common one of partnership between science and industry.

The treatment in this volume of such matters as the influence of tariffs and political economy on the industries of a country will enable the general reader to grasp certain essential factors as they are recognised to-day by the contending schools. Chapters on finance and industry, and science and industry, are equally valuable as an introduction to these complicated and involved relationships, which are so little understood in certain quarters where they should really be mastered in detail. Not the least satisfactory feature of this volume is the reprinting, with notes

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