Chapter I: The Industrial Scene, 1842 (2)

For example, there was the Anti-slavery Campaign in which Joseph Sturge and other Quakers played so prominent a part. By an organized crusade of political education the Abolitionists induced an originally hostile Parliament to emancipate the West Indian negroes in 1833, and to shorten the period of semi-servile apprenticeship in 1838. Yorkshire was the home of the Short Time Committees, which organized the campaign against White Slavery at home. The Ten Hours Movement caused the Ten Hours Bill to become the law of the land. From Lancashire came the Anti-Corn Law League, whose story is told in another chapter.

The second class of association was the association for economic betterment--the Friendly Society, the Co-operative Society, the Trade Union. Conceived in enthusiasm and self-inspired, these associations asked only of the State a legal framework in which to develop, but they did not win it without struggle and delay.

The Government was anxious to encourage thrift, but the development of the Friendly Societies was impeded for a time by legislation aimed at political conspiracy. The Corresponding Societies Act of 1799 prevented the Friendly Societies from forming a central organization with branches, and the Dorchester Labourers of 1834 discovered the peril into which the ritual of oaths might lead innocent men.

These deterrents were removed by enabling legislation. In 1829 a central authority, the Registrar of Friendly Societies, was appointed to supervise Friendly Societies, and between 1829 and 1875 further privileges and safeguards were conferred. But the Friendly Society Movement throughout the nineteenth century was wholly voluntary. In 1911 the situation was suddenly reversed by the passing of the National Insurance Act.

The Co-operative Societies were more suspect. They crept into legal recognition as the children of the Friendly Society, under the 'frugal investments' clause of the Act of 1846, being compelled by the legal prejudice against association in restraint of trade to adopt this unnatural mother. Their real nature was recognized in 1852, when they were brought under the Industrial and Provident Societies Act, and in 1862, when they were granted the boon of limited liability. But the accident of their legal origin still survives; for they are regulated to-day by the Industrial and Provident Societies Act of 1893. The Co-operative Movement is now drawing closer to politics, following the lead of most of the continental countries, notably Belgium and Germany. Though we cannot say that there is any indication of the State taking over the movement, we may note that the growth of municipal trading in the 'nineties was, in principle, an application of the consumers' association to monopolies of distribution such as tramways, water, electricity, and gas.

The State was altogether hostile to the growth of the Trade Union. The Charter of Emancipation, won by the guile of Francis Place in 1824, was severely curtailed in 1825. Huskisson[68] depicted in lurid terms the tyranny of a military trades unionism, 'representing a systematic union of the workers of many different trades'. It was a 'kind of federal republic', whose mischievous operations, if not checked, would keep the commercial classes 'in constant anxiety and fear about their interests and property'. Arnold, of Rugby, a decade later wrote of them in the same strain: 'you have heard, I doubt not, of the trades unions; a fearful engine of mischief, ready to riot or assassinate; and I see no counteracting power.'[69]

The counteracting power was their own weakness. The early militancy burnt itself out, and was succeeded at the turn of the century by a 'New Spirit and a New Model'. The new spirit was anti-militant, and the new model was a trade union representing the _elite_ of the skilled trades. The Amalgamated Society of Engineers was founded in 1850 and served as a model to the Carpenters, Tailors, Compositors, Iron-founders, Brick-layers, and others. The Trades Unions were now respectable, and in 1867 the State recognized the fact.

The period of collectivism is denoted by the growth of the Labour Party in Parliament, and the increasing part played by the State in industrial disputes and the regulation of wages. The nationalization of railways and the nationalization of mines are burning questions.

4. In all the movements we have described, the spiritual stimulus, the initial drive, and the solid successes have been provided by voluntary association. The State has not been the pioneer of social reform. Such a notion is the mirage of politicians. It has merely registered the insistent demands of organized voluntary effort or given legal recognition to accomplished facts. This is the distinctive note of English social development in the nineteenth century.

FOR REFERENCE

Dicey, _Law and Opinion_.

Robinson, _The Spirit of Association_.

Hovell, _The Chartist Movement_.

Sombart (tr. Epstein), _Socialism and the Socialist Movement_.

[Cd. 9236], _Report of Committee on Trusts_.

FOOTNOTES:

[Footnote 20: From the writer's forthcoming book _Life and Labour in the Nineteenth Century_, to be published by the Cambridge University Press.]

[Footnote 21: Tooke and Newmarch, _History of Prices_, v. 356.]

[Footnote 22: _Commons Committee on Emigration_, 1827, Q. 1761.]

[Footnote 23: _Commons Committee on the Condition of Labourers employed in the Construction of Railways_, 1846, Q. 866.]

[Footnote 24: Ibid., Q. 217.]

[Footnote 25: Ibid., Q. 897.]

[Footnote 26: Ibid., Q. 733.]

[Footnote 27: Ibid., Q. 193.]

[Footnote 28: Ibid., Qs. 869-78.]

[Footnote 29: _Report of Poor Law Commissioners on the Employment of Women and Children in Agriculture_ (1843), pp. 20, 25.]

[Footnote 30: Ibid., pp. 299-300.]

[Footnote 31: _Report of Commissioners on the Employment of Young Persons in Agriculture_, p. 64.]

[Footnote 32: Dr. Cook Taylor, Letter to the _Morning Chronicle_, dated from Rossendale Forest (Lancashire), June 20, 1842.]

[Footnote 33: _Rural Rides_, i. 219.]

[Footnote 34: _Poor Law Commission of 1834_, Appendix.]

[Footnote 35: _Hand-loom Weavers' Commission, Final Report, 1841_, p. 18.]

[Footnote 36: _Hand-loom Weavers' Commission, Assistant-Commissioner's Report, 1840_, Part IV, pp. 76-81.]

[Footnote 37: _Second Annual Report of the Poor Law Commissioners_, 1836.]

[Footnote 38: _Hand-loom Weavers' Commission, Assistant-Commissioner's Report_, Part III, p. 551.]

[Footnote 39: _Anti-bread Tax Circular_, No. 91, June 16, 1842.]

[Footnote 40: _First Report of the Factory Commissioners_, 1833, p. 27.]

[Footnote 41: _Report of Commissioner on the Condition of the Framework Knitters_ (1845), p. 109.]

[Footnote 42: Ibid., p. 115.]

[Footnote 43: William Felkin, _History of the Machine-wrought Hosiery and Lace Manufactures_ (1867), p. 458.]

[Footnote 44: _Evidence before the Truck Commissioners_ (1871), Q. 37,500.]

[Footnote 45: Pamphlet of 1825, p. 14.]

[Footnote 46: _Home Office Papers_, 40, Letter from R.J. Blewitt, Esq., M.P., November 6, 1839.]

[Footnote 47: Richard Fynes, _Miners of Northumberland and Durham_, p. 72.]

[Footnote 48: John Wilson, _History of the Durham Miners' Association_ (1870-1904), p. 40.]

[Footnote 49: _Report of Commissioner on the State of the Mining Population_ (1846).]

[Footnote 50: These pamphlets are in the British Museum.]

[Footnote 51: _Report of Commissioner on the State of the Mining Population_ (1850).]

[Footnote 52: Ibid. (1852).]

[Footnote 53: _Royal Commission, First Report_ (_Mines_), p. 27.]

[Footnote 54: Ibid., p. 21.]

[Footnote 55: _Royal Commission, Second Report_ (_Trades and Manufactures_), p. 147.]

[Footnote 56: Ibid., pp. 155-6.]

[Footnote 57: _Midland Mining Commission, First Report_, p. 34.]

[Footnote 58: Ibid., p. 91.]

[Footnote 59: Ibid., p. 44.]

[Footnote 60: _Rural Rides_, ii. 353.]

[Footnote 61: _Commons Committee, Stoppage of Wages_ (_Hosiery, 1854_). Evidence of Mr. Tremenheere.]

[Footnote 62: _Evidence before the Truck Commissioners_, Q. 33,670.]

[Footnote 63: _Truck Commission, 1871. Report_, p. 16.]

[Footnote 64: _Commons Committee, Stoppage of Wages in the Hosiery Manufacture_ (1854), Q. 80.]

[Footnote 65: _Commons Committee of_ 1816, pp. 64 and 73.]

[Footnote 66: Ibid., p. 38.]

[Footnote 67: Ibid., p. 28.]

[Footnote 68: Speech, March 29, 1825.]

[Footnote 69: Letter to the Chevalier Bunsen, 1834, quoted in Strachey, _Eminent Victorians_, p. 197.]

VIII

ATOMIC THEORIES

PROFESSOR W.H. BRAGG, C.B.E., D.SC., F.R.S.

When a lecture on the progress of Science is given before a conference concerned largely with historical subjects, it is not inappropriate to point out that Science has a history of its own and that its progress makes a connected story. The discovery of new facts is not made in an isolated fashion, nor is it a matter of pure chance, unaffected by what has gone before. On the contrary, scientific progress is made step by step, each new point that is reached forming a basis for further advances. Even the direction of discovery is not entirely in the explorer's control; there is always a next step to be taken and a limited number of possible steps forward from which a choice can be made. The scientific discoverer has to go in the direction in which his discoveries lead him. When discoveries have been made it is possible to think of uses to which they may be put, but in the first instance all discoveries are made without any knowledge whatever of what use may afterwards be made of them.

Consequently scientific progress is a quite orderly advance, not a spasmodic collection of facts, and in the truest sense of the word it has a history. In order that opportunities for this steady progress may be provided it is very important that this point should be fully appreciated. Every one, for example, is vaguely conscious that science played a great part in the War. As a consequence the number of students of science has greatly increased; manufacturing firms are awakening to the fact that they must pay more attention to scientific development and are founding research laboratories. It is very important that this awakened attention should be well informed, and for that reason it cannot be pointed out too often that the scientific work which has been the basis of all material progress can only be turned to definite material ends in the last stages of its development. Fundamentally everything rests on the pure attempt to gain knowledge without any idea of the use to which it may subsequently be put. Without pure science there is no applied science at all. It is quite right in my opinion that the researcher in pure science should have with him the hope that what he does may one day be of direct benefit to others. But it is probable that he does not in his own mind confine the idea of possible uses to such material matters as I have mentioned above and as are so prominent at present. He believes that his work has a less material side whose value need not be explained to the present audience.

In the general line of progress it is natural to find that there are certain broad roads along which the main advance has been directed. Students of physics and chemistry and the subjects which are allied to them find that they are in general considering either matter, or electricity, or energy. I make this classification, not from any philosophical point of view, but simply for present convenience. The first important principle to which I would like to draw your attention is that each of these things can be measured quantitatively. If we accept the weight of a substance as an indirect measure of the amount of matter present, then we all know we can express the amount of matter in any given body in terms of a fundamental unit, like a pound or a gramme; and the idea has been put to immemorial use. In later years we have learnt that electricity itself is also a quantity and that the amount of electricity which stands on an electrified body, or flows past a given point in an electric conductor, as for example the wire connected to an electric light, can be expressed arithmetically in terms of some unit. Instruments are made for the purpose of measuring quantities of electricity in terms of the legal standard. It is one of the functions of a Government Institution, like the National Physical Laboratory, to test such instruments and report on their accuracy. International conferences have been held for the purpose of reducing these units to as small a number as possible so that people may be able to trade less wastefully and more conveniently, so that also the barriers between peoples may be broken down and the interchange of ideas as well as of materials may be made more easily. Without an arrangement of this kind it would be impossible to carry on industrial life in which use is made of electricity. It would be as difficult as to hold a market without the use of weights and scales, more difficult, in fact, since anyone can estimate the size of a piece of cloth or the amount of corn in a sack, but no one has a natural sense by which he can estimate an amount of electricity.

In just the same way energy can be measured as a quantity in terms of a fundamental unit. The discovery that this was so was made by Joule and others towards the middle of the nineteenth century, and lit the road for further advance as a dark street is lit by the sudden turning-up of the lamps. All modern industry rests on this principle. We are now so accustomed to the idea that energy is a quantity that we can hardly realize a time when it was merely a vague term. If we want an illustration of how thoroughly we have grasped this idea let us remember that when we pay our electric-light bill we pay so much money for so many units of energy supplied; for so much energy, let us note, not for so much electricity, since we take into account not only the actual amount of electricity driven through our house wires, but also the magnitude of the force which is there to drive it. Energy exists in many forms: energy of motion, heat, gravitational energy, chemical energy, radiation, and so on. In the transformations of energy which are continually occurring in all natural processes, there is never any change in the total amount of energy. This is the famous principle of the Conservation of Energy. Sometimes it is stated in the form 'Perpetual motion is impossible'.

One of the most important forms of energy is radiation. The constant outpouring by the sun of energy in this form is vital to us. The fact was obvious long ago and that is one of the reasons why light and heat have interested students of science in all ages.

There exist then three main subjects of study--matter, electricity, and energy. These themselves and their mutual relations have been, and are, the principal objects of interest to the scientific student, and from our strivings to understand them we have learnt most of what we know. All three are quantities and all are expressible in terms of units.

Now there is one point which I have thought would especially interest you. A very remarkable tendency of modern discovery shows more and more clearly that not only are these things quantities which we can express in units of our own choosing, but that Nature herself has already chosen units for them. The natural unit does not, of course, bear any exact connexion with our own. This being so, it must be of the utmost importance that we should know what these natural units are and so be able to understand what Nature is ready to tell us. Nature has chosen to speak in a certain language; we must get to know that language.

In the first place we know surely that there are natural units of matter. This was the great discovery made by Dalton in the beginning of the nineteenth century. When he found that each of the known elements, such as copper or oxygen or carbon, consisted ultimately of atoms, all the atoms of any one element being alike, he laid the foundation on which the huge structure of modern chemistry has been raised. The chemist takes one or more atoms of one element, one or more of another, and may be of a third or fourth, and he puts them together into a compound which we call a molecule. The molecule for example of ordinary salt contains always one atom of chlorine and one of sodium. Chlorine and sodium are elements, salt is a compound. Six atoms of carbon and six of hydrogen put together in a certain way make benzene. In the same way every substance that we meet is capable of analysis, showing ultimately the molecules as made up, according to a definite plan, of so many atoms of the various elements. In analytical chemistry molecules are dissected in order to discover the mode of their building; in synthetic chemistry the atoms are put together to make a molecule which is already known to have, or even may be anticipated to have, certain properties. This is the work of the chemist. Sometimes enormous forces are concerned in this pulling apart and putting together, witness the terrific power of modern explosives. But the same kind of handling by the chemist may be devoted to the delicate construction of a molecule which gives a certain colour to the dyer's vat and so pleases the eye that the great cloth industries feel the consequence, and nations themselves are affected by the flow of trade. After all, since the processes of the physical world operate ultimately through the power and properties of molecules, it is not surprising that the chemist's work in these and numberless other ways has such tremendous influence in the world.

Here then by the recognition of the units of matter which Nature has chosen for herself it has been possible to do great things.

It should be observed that the atom, in spite of its name, is not something which is incapable of all further division; it is only incapable of retaining its properties on division. When an atom of radium breaks down in the unique operation during which its singular properties are manifested, it dies as radium and becomes two atoms, one of helium, the other of a different and rare substance. It will interest you to know that the airships of the future are expected to be filled with this non-inflammable helium.

The discovery of the atomic nature of electricity came later. Faraday established the fact that in certain processes there was more than a hint that electricity was always present in multiples of a definite unit. In the process called electrolysis the electric current is driven across a cell full of liquid containing molecules of some substance. When the electricity passes there is a loosening of the bonds that bind together the atoms of the molecule, and a separation; atoms of one kind travel with the electricity across the cell and are deposited where the current leaves the cell; the other kind travel the opposite way. In this way for example we deposit silver on metal objects in electro-plating processes, or separate out the purest copper for certain electrical purposes. The striking thing which Faraday discovered was that the number of atoms deposited always bore a very simple relation to the quantity of electricity that passes. The same current passing in succession through cells containing different kinds of molecules broke up the same number of molecules in each cell. It was as if in each electrolytic cell atoms of matter and atoms of electricity travelled together. The movement of an atom meant the simultaneous movement of a definite quantity of electricity. Electricity was, so to speak, done up in little equal parcels, and an atom of matter on the move, which was termed an ion, or wanderer, carried, not a vaguely defined amount of electricity, but one of these definite parcels.

It was not, however, until the later years of the nineteenth century that the natural unit of electricity was manifested by itself and without a carrier. At a famous address to the British Association at York in 1881 Sir William Crookes described the first marvellous experiments in which this feat had been accomplished, though there was still to come a long controversy before the interpretation was clearly accepted. It is now definitely established that there is a fundamental atom of electricity which we now call the electron. As we all know electrification is of two kinds--a positive and a negative. The electron is of the negative kind. There does not appear to be a corresponding positive atom of electricity, or at least not one that is so singular in its properties as the electron. Electrons go to the making of all atoms, just as atoms go to the making of molecules. The atom which is neutral, that is, shows neither positive nor negative electrification, must contain positive electricity in some form to balance the electrons which we know it contains. When we strip an atom, as we know how to do, of one or more of these electrons, the remainder is positively charged. The positive ion is any sort of an atom or molecule which has become positively electrified in this way. An atom which has become positive by the loss of one or more of its electrons exercises a force on any spare electrons in its neighbourhood or on any atom carrying a spare electron. When there are large numbers of atoms seeking in this way to become neutral once more, as occurs often in Nature, the forces generated may be tremendous. They are shown, for example, in the lightning-stroke. But indeed it would seem that all the chemical forces of which we have already spoken depend ultimately upon the electric state of the atom concerned.

It is because the force which a positively-charged atom exerts on an electron is so great and because the electron is so light and easily moved compared to an atom that the electron has not been isolated at will until recent years. The isolation in fact depends upon the electron being endowed with a sufficient speed to carry it through or past the action of an atom which is seeking to absorb it into its system. A lump of matter flying in space might enter our solar system with such speed as to be able to pass through and go on its way almost undeflected. Or again, it might have a much lower speed and go so much nearer the sun that it was seriously deflected in its course, as we see in the case of comet visitors. But if for some reason or other the lump of matter found itself inside the solar system without the endowment of high velocity it would certainly be absorbed. Just so an electron can pass through an atom with or without serious deviation from its line of motion, provided that motion is rapid enough. Only recently have we been able to exert electric forces of sufficient strength to set an electron in motion with the speed it must have if it is to maintain an individual existence Now we can gather electrons at will, dragging them from the interior of solid bodies, and hurl them with tremendous speed like a stream of projectiles. Since in the open air the speed is soon lost by innumerable collisions with the air-molecules, the effect can only be studied satisfactorily in a glass bulb from which the air has been evacuated. Crookes made great improvements in air-pumps during an investigation on thallium, and consequently was able to obtain the high vacuum required for the experiment with the electron streams. It was afterwards found by Roentgen that when an electron stream in an evacuated bulb was directed upon a target placed within the bulb, a remarkable radiation issued from the target. Thus arose the so-called X or Roentgen rays. As you all know they have for many years played a most important part in surgery and medicine. You may have heard that during the war they were also used to examine the interior of aeroplane constructions and to look for flaws invisible from without. Although X-Rays are of the same nature as light rays they can penetrate where light rays cannot, passing in greater or less degree through materials which are opaque to visible light and allowing us to examine the interior which is hidden from the eye.

Every electric discharge is essentially a hurried rush of electrons. When we rub two bodies together and they become electrified we have in some way or other torn electrons from one of the bodies and piled them on the other. The former becomes the positively charged body and the latter the negative. A film of moisture stops this action. When wool is spun in factories it tends to become in certain stages of the process too dry and too free from grease; the yarn then becomes electrified as it passes over the leather rollers, and when the machine tries to spin the threads together they fly apart and refuse to join up the minute hooks with which the wool fibres are furnished. The spinning operation would come to an end were there not means provided by which the air can be so filled with moisture that the fibres become damp and the action ceases. So in some cases a stream of air filled with positive and negative ions is made to play upon the fibres; the fibres select what ions they want, and so neutralizing themselves, spinning can proceed again.

When a current of electricity runs along a wire there is in fact nothing more than a procession of electrons. The stream of electrons that runs through the filaments in the lamps that light this room, raising the filaments to a white heat, are set in motion by the dynamos in the city. There is a complete wire circuit, including the dynamo, the conductors, and the lamps. When the dynamos are not working the electrons do not as a whole move either way, though they are always there. When the dynamo begins to turn, the electrons set out on their continuous journey.

Electrons are involved in the emission of wireless signals, and in their receipt. The so-called 'valve', which multiplies minute electric signals and was so greatly improved during the war, depends entirely on the action of electrons, and the brilliant experimental work was based on the newly-acquired knowledge of their properties.

I have told you that under certain circumstances a stream of electrons may generate X-Rays, in reality a form of light rays. This action is a very common one, and it is curious that the faster the electron goes the shorter is the wave-length of the radiation. A very fast electron generates an X-Ray of so short a wave-length that the penetrating power of the ray, which goes with the shortness of the wave, is excessive, and in this way we may have rays which go right through the human body or even through inches of steel. As the speed of the exciting electron becomes less, the X-Rays are less penetrating. With still slower electrons we may generate ordinary light, and it will take a slower electron to generate red than to generate blue. The slowest electrons we use in this way have a speed of many hundred miles per second; the fastest have a speed which nearly approaches that of light, or 186,000 miles a second.

And conversely radiation can set electrons in motion. When X-Rays are driven into a patient's body electrons are set in motion within, and moving over certain minute distances, initiate chemical actions which are necessary to some cure. Or they may go right through the body and fall on a photographic plate, setting in operation chemical action which forms a picture on the plate.

There is another occasion of an entirely different kind when the electron is greatly in evidence and displays effects which are most astonishing and significant. Every atom of radium or other radio-active substances sooner or later meets with the catastrophe in which its life as radium ends and atoms of other substances are formed. At that moment occurs the emission which is the characteristic property of the substance. One of the radiations emitted consists of high-velocity electrons, moving, some of them, nearly as fast as light.

Now it is found that when the speed approaches that of light, 186,000 miles or 3 x 10^{10} centimetres per second, the energy is higher than it should be if it followed the usual rule, viz. energy is equal to half the mass multiplied by the square of the velocity. It would seem that an electron moving with the velocity of light would have infinite energy; or, to put the matter in another way, the experimenter in his laboratory can never hope to observe an electron moving so fast; it would be the end of his laboratory and of himself if ever it turned up.

Linked up with this result is the very strange fact that no one has ever been able to find any direct evidence of the existence of the ether, which is postulated in order to carry light-waves. It has been pictured as a medium through which the heavenly bodies move, and to which their motions may be referred. But when light is launched into the ether, its apparent velocity must depend on whether it travels with or against the drift of the ether through the laboratory where the measurement is made. The experiment has been performed without the discovery of any such difference, although the method was amply accurate enough to detect the effect that might be expected. It was afterwards shown that the negative result might be explained by supposing that a measure of length varied in length according to whether it was travelling with or against the ether. But the continual failure of all such experiments has led to a remarkable hypothetical development with which the name of Einstein is firmly connected. It is supposed that some flaw must exist in our fundamental hypotheses, and that if this were corrected we should then find that we ought to get the same value for the velocity of light however and whenever we measured it, and at the same time we should find that no measurement of the velocity of a body moving relative to the observer would ever equal the velocity of light. The hypothesis denies the existence of an absolute standard to which motions can be referred, and insists that they must all be considered relatively to the observer. It is called the principle of relativity. Calculations of its consequences begin with the necessary changes in the fundamentals, such as Einstein has introduced.[70]

Time does not allow me to say more of the innumerable ways in which electrons play an essential part in all the processes in the world. We have long believed that this is so, but the picture has never been so clear to us as it is now; and with our understanding our power is increased. Yet once more the illumination of our understanding comes from our recognition that Nature has preferred the discrete to the continuous and that electricity is not infinitely divisible but is, like matter, and even more simply than matter, of an atomic structure. And we have found the unit and learnt how to handle it.

It is even more strange that it may now be said of energy that there are signs of atomicity. It may seem absurd to think that the energy which is transformed in any operation is transformed in multiples of a universal unit or units, so that the operation cannot be arrested at any desired stage but only at definite intervals. Indeed we have no right to assert that this is always true. But undoubtedly there are cases in which the atomicity of energy is clear enough, as for example in the interchange of energy between electrons in motion and radiation. It is remarkable that when radiation sets an electron in motion, the electron acquires a perfectly definite speed depending only on the wave-length of the radiation and not on its intensity, and has apparently absorbed from the radiation a definite unit of energy. Radiation of a particular wave-length cannot spend its energy in this way except in multiples of a certain unit, because each of the electrons which it sets in motion has the same initial energy, which it must have got from the radiation. In other words, energy of radiation of the particular wave-length can only be transformed into energy of movement of electrons in multiples of a certain 'quantum' peculiar to that wave-length. The intensity of the radiation, that is to say, the amount of energy moving along the beam, can only affect the number of electrons set in motion and not the speed of any one of them. During the last few years a very extraordinary theory has been developed on the basis of these and similar facts. I doubt if it would be more profitable to give further instances at present, but I have mentioned it because it seems to show looming on the horizon of our knowledge another tendency of Nature to make use of the atomic principle.

I will only add that the whole position of physics is indeed at this time of extraordinary interest, and at any moment there may be some great discovery or illuminating thought which will explain the present startling difficulties and open up new worlds of thought.

FOR REFERENCE

Bragg, _Rays and Crystals_ (Ball & Sons).

FOOTNOTES:

[Footnote 70: Since this address was given, the results of the Eclipse Expedition to Brazil are considered to have confirmed in a satisfactory manner one of the most remarkable deductions made by Einstein from the principles which he maintains. The matter has roused so much interest that some of the leading exponents of the relativity principle have published careful accounts intended for students not familiar with it: it would therefore be superfluous to discuss the matter here.]

IX

PROGRESS IN BIOLOGY DURING THE LAST SIXTY YEARS

PROFESSOR LEONARD DONCASTER, F.R.S.

On November 24, 1859, _The Origin of Species_ was published, and this date marks the beginning of an epoch in every branch of biology. Before it, Biology had been almost entirely a descriptive science, but within a few years after the publication of the _Origin_ its effects began to colour all aspects of biological research. A co-ordinating and unifying principle had been found, and the leading idea of biologists ceased to be to describe living things as they are, and became transformed into the attempt to discover how they are related to one another. The first effect of this change of attitude was chiefly to turn biologists towards the task of tracing phylogenetic or evolutionary relationships between different groups of animals--the drawing up of probable or possible genealogical trees and the explanation of natural classification on an evolutionary basis. When once, however, the notion of cause and effect, or more correctly of relationship, between the phenomena seen in living beings had become familiar to biologists, it spread far beyond the limits of tracing genealogical connexions between different animals and plants. It made possible the conception of a true Science of Life, in which every phenomenon seen in a living organism should fall into its true place in relation to the rest, and in which also the phenomena of life should be correlated with those discovered in the inorganic sciences of Chemistry and Physics.

The history of the various branches of biological science in the past sixty years reflects the general course of these tendencies. Until shortly after 1859, the study of morphology, or the comparative structure of animals (and of plants) was intimately related with that of physiology, that is, with the study of function. In the years following the appearance of the _Origin_, however, anatomists and morphologists were seized with a new interest. For the time at least, the chief aim in studying structure was no longer to explain function, but rather to explain how that structure had come into being in the course of evolution, and how it was related with homologous but different structures in other forms. The result was a tendency to a divorce between morphology and physiology, or at least between morphologists and physiologists, which led to the division into two more or less distinct sciences of what had hitherto been regarded as closely inter-related branches of one. The greater men of the early part of the period, such as Huxley, remained both morphologists and physiologists, but most of their followers fell inevitably into one or the other group, and in discussing the later phases of biological progress it will be necessary to keep them separate.

Apart from its effect on the systematic and anatomical side of Biology, the idea of Evolution, and especially of Darwin's theory of Natural Selection, had important consequences on that side of the science which may be described as Natural History. Before the appearance of Darwin's work, Natural History consisted chiefly in the observation and collection of facts about the habits and life-history of animals and plants, which as a rule had no unifying principle unless they were used, as in the Bridgewater Treatises, to illustrate 'the power, wisdom, and goodness of God'. Now, however, a new motive was provided--that of discovering the uses to the organism of its various colours, structures, and habits, and the application of the principle of natural selection to show how these characters conduced to the preservation and further evolution of the species. And out of this interest in the theory of natural selection grew in the last twenty years of the nineteenth century the greatly increased attention to the facts and theories of heredity, which was stimulated by Darwin's hypothesis of Pangenesis and especially by Weismann's speculations about the nature and behaviour of the 'germ-plasm'. Before the appearance of Weismann's work, the germ-cells, which bear somehow or other the hereditary characters that appear in the offspring, were supposed to be produced directly from the body of the parent. Darwin provisionally suggested that every cell of every organism gives off minute particles which become congregated in the germ-cells, and that these cells thus contain representative portions of all parts of the parent's body. Weismann, on the basis of his work on the origin of the germ-cells in Medusae and Insects, maintained that these cells are not derived from the body, but only from pre-existing germ-cells stored within it--that, in fact, although an egg gives rise to a hen, a hen does not give rise to an egg, but only keeps inside her a store of embryonic eggs which mature and are laid as the time comes round. The theory had to be modified to suit the facts of regeneration and vegetative reproduction, but in essence it was accepted by the biological world and is the orthodox opinion (if such a word may be used in Science) at the present day. The difference between the two views is not only of theoretical interest, for it involves the whole question of whether characteristics acquired by an individual during its life in response to external conditions can or cannot be transmitted to offspring. If the germ-cells contain representatives of all parts of the body, modifications impressed on the body during its life may at least possibly be transmitted to offspring born after the modifications have taken place. If, however, the germ-cells are independent of the rest of the body, and only stored within it for safe-keeping like a deed-box in the vaults of a bank, it would seem impossible for any environmental influence, whether for good or ill, to take effect on the offspring. This controversy on the heritability of 'acquired characters' was one of the most important towards the end of last century, and although the majority of biologists now follow Weismann in so far as they deny that 'acquired' characters are transmissible, the question is not yet completely settled; all that can be said is that, in spite of many attempts to prove the contrary, there is no satisfactory evidence of the transmission to offspring of effects impressed on the body of the parent, unless the germ-cells themselves have been affected by the same cause--as for example in some cases of long-continued poisoning by alcohol or similar drugs.

While the problem of the transmission of acquired characters, and of the cause of variation and its relation to evolution, was occupying much of the attention of biologists, the whole problem entered upon a new phase in the year 1900 with the re-discovery of Mendel's work on heredity. Mendel worked with plants, and published his results in 1865, but at that time the biological world was too much occupied with the fierce controversy which raged over _The Origin of Species_ to take much notice of a paper the bearing of which upon it was not appreciated. Mendel's discovery never came to the notice of Darwin, was buried in an obscure periodical, and remained unknown until many years after the death of its author. In 1900 it was unearthed, and, largely owing to the work of Bateson, it rapidly became known as one of the most important contributions to Biology made during the period under review.

This is not the place to describe in detail the nature of Mendel's theory. Its essence is, firstly, that the various characteristics of an organism are in general inherited quite independently of one another; and, secondly, that the germ-cells of a hybrid are pure in respect of any one character, that is to say, that any one germ-cell can only transmit any unit character as it was received from one parent or the other, and not a combination of the two. This leads to a conception of the organism as something like a mosaic, in which each piece of the pattern is transmitted in inheritance independently of the rest, and in which any piece cannot be modified by association with a different but corresponding piece derived from another ancestor. It is impossible to say as yet whether this conception at all completely represents the nature of the living organism, but it is one which is exercising considerable influence in biological thought, and if established it will mark a revolution in Biology hardly inferior to that brought about in Physics and Chemistry by the discovery of radio-activity.

An important consequence of the advance in our knowledge of heredity associated with the work of Mendel and his successors is a tendency to doubt whether natural selection is of such fundamental importance in shaping the course of evolution as was supposed in the years of the first enthusiasm which followed the publication of the _Origin_.

Darwin based his theory of Natural Selection on the belief which he derived from breeders of plants and animals, that the kind of variation used by them to produce new breeds was the small and apparently unimportant differences which distinguish a 'fine' from a 'poor' specimen. He supposed that the skilled breeder picked out as parents of his stock those individuals which were slightly superior in one feature or another, and that by the accumulative effect of these successive selections not only was the breed steadily improved, but also, by divergent selection, new breeds were produced. Experience shows, however, that although this method is used to keep breeds up to the required standard, it is rarely, if ever, the means by which new breeds arise. New breeds commonly come into existence either by a 'sport' or mutation, or by crossing two already distinct races, and by selecting from among the heterogeneous descendants of the cross those individuals which show the required combination of characters. And it is further found that most of the distinguishing features of various breeds of domestic animals and plants are inherited according to Mendel's Law, suggesting that each of these characters is a unit, like one piece of a mosaic, independent of the rest. Now it is easy to see how the selection of small, continuously varying characters could take place in Nature by the destruction of all those individuals which failed to reach a certain standard, but it is much more difficult to understand how natural selection could act on comparatively large, sporadic, unco-ordinated 'sports'. There is thus a distinct tendency at present to regard natural selection as less omnipotent in directing the course of evolution than was formerly supposed, but it must be admitted that no very satisfactory alternative hypothesis has been suggested. Some have supposed that there is a kind of organic momentum which causes evolution to continue in those directions in which it has already proceeded, while others have postulated, like Bergson, an _elan vital_ as a kind of directive agency. Others again have reverted towards the older belief in the inherited effects of environment--a belief which, in spite of the arguments of Weismann and his followers, has never been without its supporters. The present condition of this part of biology, as of many others, is one of open-mindedness approaching agnosticism. There is dissatisfaction with the beliefs which satisfied the preceding generation, and which were held up almost as dogmas, but there is no clear vision of the direction in which a truer view may be sought.

Before leaving this side of the subject, reference must be made to one important aspect of modern work on heredity--that of the inheritance of 'mental and moral' characteristics. As a result of the work of the biometric school founded by Galton and Pearson, it has been shown that the so-called mental and moral characteristics of man are inherited in the same manner and to the same extent as his physical features. Of the theoretical importance of this demonstration this is not the place to speak; its practical value is unquestionable, and may in the future have important effects on sociological problems.

Another notable line of advance, entirely belonging to the period under review, and chiefly the product of the present century, is seen in the science of Cytology--the investigation of the microscopic structure of the cells of which the body is composed. The marvellous phenomena of cell and nuclear division have revealed much of the formerly unsuspected complexity of living things, while the universality of the processes shows how fundamentally alike is life in all its forms. In recent years great progress has been made in correlating the phenomena of heredity and of the determination of sex with the visible structural features of the germ-cells. Weismann attempted a beginning of this over thirty years ago, but the detailed knowledge of the facts was then insufficient. Since the discovery of Mendel's Law, a great amount of work has been done, chiefly in America, by E.B. Wilson and T.H. Morgan and their pupils, on tracing the actual physical basis of hereditary transmission. Although the matter is far from being completely known, the results obtained make it almost indubitable that inherited characters are in some way borne by the _chromosomes_ in the nuclei of the germ-cells. The work of Morgan and his school has shown that the actual order in which these inherited 'factors' are arranged in the chromosomes can almost certainly be demonstrated, and his results go far to support the conception of the organism, referred to above, as a combination or mosaic of independently inherited features.

It was said at the beginning of this sketch that most of the more notable lines of advance in Biology could be traced back to the impetus given by the acceptance of the theory of Evolution, and the desire to test and prove that theory in every biological field. It is most convenient, therefore, to take this root-idea as a starting-point, and to see how the various branches of study have diverged from it and have themselves branched out in various ways, and how these branches have often again become intertwined and united in the later development of the science.

Perhaps the most obvious method of testing the theory of evolution is by the study of fossil forms, and our knowledge of these has progressed enormously during the period under review. Not only have a number of new and strange types of ancient life come to light, but in some cases, e.g. in that of the horse and elephant, a very complete series of evolutionary stages has been discovered. In this branch, however, as in almost all others, the results have not exactly fulfilled the expectations of the early enthusiasts. On the one hand, evolution has been shown to be a much more complex thing than at first seemed probable; and on the other, many of the gaps which it was most hoped to fill still remain. A number of most remarkable 'missing links' have been discovered, such as, for example, _Archaeopteryx_, the stepping-stone between the Reptiles and the Birds, and the faith of the palaeontologist in the truth of evolution is everywhere confirmed. But the hope of finding all the stages, especially in the ancestry of Man, has not been realized, and it has been found that what at one time were regarded as direct ancestors are collaterals, and that the problem of human evolution is much less simple than was once supposed.

A second important piece of evidence in favour of evolution is provided by the study of the geographical distribution of animals, on which much work was done in the earlier part of the period under review. And in this connexion mention must be made of the science of Oceanography, for our whole knowledge of life in the abysses of the ocean, and almost all that we know of the conditions of life in the sea in general, has been gained in the last fifty years.

Another of the chief lines of evidence for the truth of the evolution theory is based on the study of embryology, and this also was followed with great vigour by the zoologists of the last thirty years of the nineteenth century. It is found that in many instances animals recapitulate in their early development the stages through which their ancestors passed in the course of evolution. Land Vertebrates, including man, have in their early embryonic life gill-clefts, heart and circulation, and in some respects skeleton and other organs of the type found in fishes, and this can only be explained on the assumption that they are descended from aquatic fish-like ancestors. On the basis of such facts as these, the theory was formulated that every animal recapitulates in ontogeny (development) the stages passed through in its phylogeny (evolution), and great hopes were founded upon this principle of discovering the systematic position and evolutionary history of isolated and aberrant forms. In many cases the search has led to brilliant results, but, as in the case of palaeontology, in many others the light that was hoped for has not been forthcoming. For it soon became evident that the majority of animals show adaptation to their environment not only in their adult stages but also in their larval or embryonic period, and these adaptations have led to modifications of the course of development which are often so great as to mask, or obscure altogether, the ancestral structure which may once have existed. Although, therefore, the results of embryological research have provided most convincing proof of the truth of the theory of evolution in general, they have not completely justified the hopes of the early embryologists that by this method all the outstanding phylogenetic problems might be solved.

The detailed study of embryology, however, has led to most important results apart from the particular purpose for which most of the earlier investigations in this field were originally undertaken. For the study of embryology, at first purely descriptive and comparative, was soon found to involve fundamental problems concerning the factors which control development. An egg consists of a single cell, and it develops by the division of this cell into two, then into four, eight, and so forth, until a mass of cells is produced. In some cases all these cells are to all appearance alike, or nearly alike; in others the included yolk is from the first segregated more or less completely into some cells, leaving the other cells without it. But in any case, after this process of cell-division has proceeded for a certain time, differentiation begins to set in--some cells become modified in one way, others in another, and from what was a relatively homogeneous mass an organized embryo, with highly differentiated parts, appears. The problem immediately propounds itself--what are the factors which control this differentiation? This problem is essentially a physiological one, and yet, since it arises most conspicuously in a field which has been worked by professed zoologists rather than physiologists, it has been studied more by those trained in zoology and botany than by those who have specialized in physiology. In this way, as in many other directions, such as in the study of heredity, of sex, and of the effects of the environment on the colours and structure of animals, the trend of zoology in recent years has returned towards the physiological side, and the old division which separated the sciences (but which has never so seriously affected students of plant life) is being obliterated.