Part 13

Man is a social animal, and his natural strength lies in community of action with his fellows. It is this which gives music its power over masses of men, the pulsation of the drum, the blare of the answering trumpets, or the strident voice of the bagpipe cry to them in tones which cannot be misunderstood, binding them into a brotherhood of courage and obedience. But a society of Morris Dancers does not need to be reminded of the noble effect of human movement controlled by music. The word 'caper' has somewhat ridiculous associations, but we have learned to respect it for what it implies: the finely ordered strenuous movement of strong bodies leaping in rhythmic dance. It suggests something pagan and prehistoric, a physical religion of astonishing beauty. Some of our Morris men are now giving all the vigour of their young bodies to a great and just cause. Let us wish them a victorious home-coming.

XII THE TEACHING OF SCIENCE {201}

It is not difficult to sympathise with what Dr. Birkbeck aimed at in founding the College which bears his name. His idea seems to have been, that whatever a man's calling may be, he is the better for accurate knowledge of the things with which he deals. This is a sufficiently obvious statement. But if for the word 'accurate' we substitute 'scientific,' it is no longer a platitude--at least it is not so in the ears of the semi-educated. For we can still find people who believe in the "practical man" as opposed to one whom they probably call a scientist. One would like to know more of the conception of science formed by the unscientific. They are probably unaware that science is eminently practical in asserting that only to be true which rests on wide and accurate generalisation. It is also practical wisdom to hold, as science does, that truth is temporary and relative, and is in fact merely the best conclusion that can be drawn in the present state of knowledge. To many people science is wearisome and somewhat ridiculous, and these qualities appear in the naturalist of fiction. Thus when even George Eliot draws a coleopterist, he is made a feeble old man shuffling to and fro among his ridiculous beetles. And on the French stage I have seen a botanist treated in the same spirit.

Positiveness and bumptiousness are also supposed to be our attributes. In the 'New Republic' the characters said to represent Huxley and Clifford are completely disguised by their pompous pretentiousness.

It is not difficult to describe the ideals of science, but it is only too easy to fall short of them. It is easy for instance to become a sectarian, to belong to a school, and to be literally incapable of fairness towards the opposition. This was plainly seen at the incoming of evolution, and it was one of the many glories of Sir Charles Lyell that he could accept the 'Origin of Species,' and that, in the words of Hooker, he could under-pin his work with an evolutionary foundation and find his edifice stronger than ever. But we need not consider the battles of giants; we are much more likely to be concerned with the mentally dwarfed or deformed--with the dangerous man who makes positive statements on insufficient data, or suffers from that other vice of not being able to confess ignorance. The only lectures which impressed me, as an undergraduate at Cambridge, were those of the late Sir George Humphry; and his most striking words were confessions of complete ignorance about many parts of physiology. Here is an instance of an opposite state of things, of a want of courage. An eminent chemist was asked why common salt thrown on the fire gives a blue flame. Now the chemist was a German, and having been brought up in that land of stoves, probably had not performed an experiment so easily made in the home of open fires. So he rashly answered, "It does not burn blue, it is impossible, sodium-salts give a yellow flame." On this my friend fetched the salt and threw a handful on to the glowing coals--with the result that the eminent chemist rose up and fled in silence from the room. He gave an admirable example of how not to behave. He ought not in the first place to have denied the fact _a priori_, and when he was convicted he should have been glad to learn.

It has been said that in scientific work accuracy is the most valuable quality and the hardest to attain. Accuracy alone may strike us as a dull quality to be so highly rated. When a given result has been obtained in eleven successive experiments, and fails on the twelfth occasion, it is the accurate-minded man who makes a wise use of the failure. It ought to arouse in us a flame of curiosity, lighting in us a whole posse of theories, which force us to vary our procedure and finally enable us to solve the difficulty.

Most of us are inclined to treat an unexpected result in a cavalier spirit, pushing it aside as "only an exception," whereas it should be received as possibly a personage of distinction in disguise, and not as a rude disturber of our pet ideas.

A class of experimentalists exists from whom we all suffer--namely, cooks. How happy we should be if they possessed this lively desire to understand their own lapses from good cookery! It may be urged in excuse, that although the essence of cooking is the application of heat to food, not one cook in a thousand has a thermometer in her oven. I hope that some of the ladies who have in these laboratories learned to believe in accuracy, will become missionaries among the ignorant and insist on this simple reform.

There is a type of accuracy of a very different kind which may become an actual vice. For instance, the desire to weigh things to 1-10 mg. which should only have been weighed to a centigram, measuring to 1-10 mm., and calculating averages to several places of decimals. In such a science as Botany this may be positive waste of time. Sachs, the great German botanist, in whose laboratory I worked, was never tired of complaining of this "sogenannte Genauigkeit," (this so-called accuracy). I am told that Lord Rayleigh, whose physical inquiries demand in some cases excessive and minute accuracy, has a wonderful instinct for knowing when and where he may relax his methods.

I have been compelled to use the words 'science' and 'scientific' because these terms have become firmly adherent to a group of subjects such as Physics, Chemistry, Geology, Botany, etc., and cannot now be detached from them. Unfortunately 'scientific' is used in another sense as implying accuracy of experimental method and in deduction from results. So that in calling ourselves scientific men we run the risk of seeming to claim a monopoly of method, as though we pretended to be somehow superior to the trained workers in other branches. The current use of the word seems therefore to cast unjust suspicion on literature. I wish that the word _science_ could be restored to its original meaning of knowledge, or the art of knowing; but words (like organisms) are evolved, and against evolution the gods fight in vain. In any case I hope it will be believed that in speaking of knowledge I have taken instances from what is usually called science, not out of disrespect to literature, but like Dr. Johnson in a different affair--from ignorance.

I imagine Dr. Birkbeck to have had no idea that this institution would be so extensively used for preparing people for examinations. I doubt whether he would have liked it, but respect to the pious memory of a founder may be exaggerated, and since there is no getting rid of examinations, the next best thing is to make the art of coaching as little harmful as may be to pupil and teacher. I do not mean to speak slightingly of coaching as a whole, for a great deal of it is only a very skilful way of imparting knowledge, but it will be allowed that some of it is not educative in a broad sense.

You will remember that Mr. Brooke, in _Middlemarch_, was in the habit of mildly investigating questions which he always threw over because he foresaw they would "carry him too far." I confess to feeling very like Mr. Brooke when I attempt to balance the interests of teacher and student. In that comfortable period, the 18th century, things were all in favour of the teacher. The poet Gray, who was Professor of History at Cambridge, could never decide whether to lecture in Latin or English, and ended by never lecturing at all.

It is now easier to find cases where the teacher is the victim and slave of his pupils, and has no time or strength to continue his own education.

This has at least two bad results, and probably more than that number: (1) From want of time for reading the teacher can hardly avoid falling behind in a rapidly progressive subject such as one of the natural sciences, and consequently the University or College that enslaves him is injuring its own property. (2) He has no time to do any original work, and this is even worse for him (and therefore, as before, for the College). He ceases to be on intimate terms with the plants or animals or chemical substances with which he has to deal, and his teaching must necessarily lose that vigour and freshness that comes from first-hand personal knowledge. It is downright cruelty to deny time for research to those who vehemently desire to add something to the fabric of human knowledge.

The hampered teacher reminds me of a certain migratory bird living with clipped wings in a Zoological Garden: when the migrating season came round the unfortunate prisoner started to walk, and was to be seen pressing its breast against the bars at the north end of its pen. I hope that nowadays all Colleges realise that they must not prison their birds, but give them the means of satisfying their natural instinct for fresh and self-gained knowledge. The students are in one way better off than their masters, since laboratory work is generally new to them and has therefore some of the charm of discovery.

In what I have said to-night I have confined myself to Natural Science, in which alone I have had experience of teaching or examining. On the literary side of things I am, I fear, a Philistine, or _enfant terrible_. I belong to that class of persons (which has at least the merit of being very large) who have hardly opened a Greek or Latin book since the day they passed their Little-go.

I grudge the time that is given at school to making small boys groan over books not well suited to them, while French and German are, or were in my day, all but untaught. If I had had good oral teaching in modern languages (such, for instance, as that given at the Perse School in Cambridge) I could forgive my teachers. We should without tears have learned to talk fluently and write correctly in at least one modern language, and for the sake of this I could perhaps have borne the weariness of Greek and Latin grammar. If it were not for the tyranny of examinations, classical teaching might be put to its proper use, which is not to serve as an instrument of torture, but to enable us to read ancient authors.

I would teach Latin and Greek only to older boys, and by the method in which we all learn a modern language--that is when we have the advantage of being at once teacher and learner. I mean by reading quickly, with a translation if necessary; at first without understanding half of what we read, but gradually picking up words as we go along. This is how I learned to read easy Italian. By the advice of the late Henry Sidgwick I began on a bad Italian translation of a French novel, because such a version, being full of French idioms more or less literally translated, is easier than idiomatic Italian. The right book to begin on is a good murder story, such as one of Gaboriau's, which are fortunately to be had in bad Italian. What would an old fashioned teacher of Greek and Latin have said to this! In my own case I feel that the _difficulty_ of reading the classics was good discipline, and so far educational. In Henry Sidgwick's method one is carried along by the detective business, and learns Italian words as a child picks up its own language, by context and re-iteration. It will be said that this method is not applicable to Latin and Greek, and that even if it were so, it would not be educative. I confess I do not expect my words to sink into the hearts of the teachers of what are unkindly called the dead languages. The great Moloch of examination has constantly to be supplied with human children, to say nothing of grown-up people. Some escape, but how many are reduced to ashes?

I have said nothing about what should have been my theme, namely, the beginning of the College year. To my thinking beginnings have something of the melancholy that seems more appropriate to endings. Sad associations tend to adhere to all that has the quality of periodicity. I for one feel this when spring once more puts on the familiar look with which our childhood and youth seemed to mingle on equal terms, but which upbraids us now we are no longer young.

And in a more work-a-day spirit Monday morning is sad. I think this is so because the conception Next Week is full of the ghosts of dead resolutions. No doubt it was on Monday mornings that Mr. Shandy renewed his vow to have the hinge of the parlour door mended, which I think remained unrepaired to the end of the book.

But after all, this gloomy point of view belongs to the onlooker, not to the actors in the rhythm of things. Each particular Monday is a new-born entity, and doubtless feels a pleasurable excitement in its brief life. And to the actual snowdrops and winter aconites that pierce the cold ground, spring is a new and glorious experience. In this academic springtime (which chances to occur in autumn) the onlooker need have no morbid feelings, only perhaps a touch of envy of those whose College life begins to-day.

XIII PICTURESQUE EXPERIMENTS

To those who have never made experiments on plants it may seem that 'picturesque' is an odd term to apply to laboratory methods. But to an experimentalist the adjective does not seem overstrained. There is not merely the pleasure of seeing a prediction verified--that may be experienced in more everyday matters. There is a peculiar delight in the discovery of a method of revealing some detail in the natural history of living things. I remember vividly the pleasure which I felt when I first tried the experiment on _Sorghum_, described in the essay on the Movements of Plants in this volume. {210} I hoped that the seedlings would curve in the elaborate manner shown in Fig. 4. But I had so little expectation of success that I did not explain the object of the trial to my laboratory assistant, and it came as a shock of delight when he told me that the seedlings had "curled up like corkscrews." I do not think that it is an exaggeration to say, that this result is a picturesque illustration of the distribution of gravitational sensitiveness in plants. The instances in the present essay are not concerned with the movements of plants, and are so far less interesting, but I think the reader will not refuse them the same adjective.

We all know that in plants--from the smallest weed to the giant trees of America--there flows a stream of water from the root to the topmost leaf. Nevertheless, it is an experience to have ocular proof of this life-giving current. A branch of laurel is so arranged that it has to suck up the water it needs through a coarse thermometer tube, dipping into a beaker. The laurel does not wither, and we know therefore that it is continuously supplied with water. If the beaker is removed we shall see the absorption, for the thermometer tube does not remain full of water; a minute column of air is seen at its lower end which rapidly increases in size, and finally when the tube is emptied of its water-content, bubbles of air escape one after another into the larger tube, which contains the cut end of the branch. This, the simplest possible experiment, is nevertheless a vivid ocular proof of the laurel's power of absorbing water. It can be shown that the sucking power of the branch depends on its leaves, for if these are removed the rate of the current is very greatly diminished. It can also be proved that it depends on some quality of the leaf surface, for if a new specimen is taken, and if the lower sides of its leaves are rubbed with vaseline, the rate of absorption will be seen to diminish very greatly. Greasing the upper surface of the leaves does not produce this result, and when we examine the two surfaces it is found that the lower one is riddled with innumerable microscopic holes (stomata), while the upper side of the leaf has no such apertures. The stomata in fact are the arbiters of what shall pass in or out of the body of the leaf; they are the gate-keepers who regulate both export and import. They are known by actual inspection (with a microscope) to close at night: the result of this is that the evaporation of the leaves is much slower at night, and this is true when allowance has been made for the fact that evaporation is also checked at night by the dampness of the air.

[Picture: Fig. 7. The Porometer]

The microscopical inspection of stomata is not a completely satisfactory method of discovering to what degree they are open. It has, however, been my good fortune to resuscitate and simplify a method of studying the stomatal condition. The method was many years ago tried in a hopelessly cumbersome form by a German, but never came into use. My apparatus is described in the _Proceedings of the Royal Society_, {212} and is known as the Porometer. Its essential part is shown in Fig. 7. It consists of a funnel-shaped tube, having a broad flange, which is cemented on to the stomata-bearing surface of a leaf. The leaf is represented by the obliquely shaded object and is enormously magnified. To the upper orifice of the funnel is fixed a rubber tube, and by means of it steady suction can be supplied. The result is that a current of air is drawn through the stomata into the leaf, and then out of the leaf into the cavity of the porometer. The rate of this current is an index of the degree to which the stomata are open. With this apparatus a number of interesting points can be determined.

[Picture: Fig. 8. Curve of Porometer readings in light and darkness (black)]

Fig. 8 shows the effect of alternate periods of light and darkness. The fall of the curve represents partial closure, and is seen to occur in the periods of darkness (black), and to rise when the plant is re-illumined. These changes are necessarily accompanied by rise and fall in the evaporation of the leaf, but into the question of the accuracy of this correlation I shall not enter.

There are other methods of demonstrating the movements of the stomata. Stahl had the happy inspiration of making use of the colour-changes of cobalt chloride. A piece of filter paper soaked in a 5 p.c. solution of this salt is blue when dried, and turns pink in damp air. A dry piece of this material, applied with proper precaution to the stomata-bearing surface of a leaf, rapidly changes to pink if the stomata are open. When, however, the same trial is made on the upper surface of a leaf, where stomata do not occur, no such change occurs. If two leaves are treated at the same time, one in the normal position and the other upside down, it is delightful to watch the appearance of a pink picture of that leaf whose stomatic surface is in contact with the paper, while no such change takes place over that which exposes no stomata to the tell-tale material. Another method was discovered by the accident of finding in an old house in Wales a Chinese figure of a man, cut out of a thin shaving of horn, which writhed and twisted when placed on the hand. It was clearly very sensitive to moisture, and it seemed possible that horn-shavings might be used to test the condition of the stomata. The first difficulty was to obtain a supply of this material. Having discovered from the P.O. Directory that there were two horn-pressers in London I proceeded to visit one of them somewhere in Hoxton. He turned out to be of a highly suspicious disposition, but his wife had more discernment, and persuaded him that I was a harmless customer, with no designs on trade secrets, and I finally obtained what I wanted. A delicate strip of horn was fixed to a little block of cork and placed on a leaf, and to my delight showed the stomata to be open by violently curving upwards. It was only necessary to fix a graduated arc to the cork, and to fasten a delicate hair on to the horn so as to serve as index. The instrument is not of course accurately quantitative, but it does at least show whether the stomata are nearly shut, moderately open, or widely so. Rough as it is I found it good enough for determining a number of interesting facts in the physiology of stomata. {215a}

I now pass on to a different subject, the all-important process on which the life of green plants depends, an act therefore by which our own existence and that of all other animals is conditioned. I mean the process known as _assimilation_. This is the truly miraculous feat of using as a source of food the carbonic acid gas (CO2) which exists in minute quantities in the atmosphere. The plant is in fact a carbon-catching machine, and the machine is driven by the energy of the sun, and can therefore only work in light. The eminent Russian botanist, Timiriazeff, in a lecture on this subject {215b} before the Royal Society, made a witty use of _Gulliver's Travels_--a book not commonly quoted as an authority in scientific matters. He pointed out that the philosophers of Lagado, who were extracting sun-beams from cucumbers, were not doing anything absurd. On the contrary, since the cucumbers had been built with the help of sunshine, it was a reasonable expectation that energy corresponding to the sunshine should be obtainable. This indeed is what we do when we drive a steam engine by burning coal which ages ago was built by vegetable machinery driven by sunlight.

It is possible to show the existence of this process by very simple experiments. The most direct, but the least interesting, experiment is to take two similar plants, and expose plant _A_ to an atmosphere containing CO2 while _B_ is in air freed from that gas. Both specimens are placed in bright light, and after a sufficient interval of time their leaves are tested for the presence of starch. This is a simple matter; the green colouring matter is washed out of them by means of alcohol, and they are then placed in a dilute solution of iodine, which has the property of staining starch purple. It is always pleasant to see the leaf that had been supplied with CO2 turn blue, while the starved leaf remains a hungry yellow.