Darwin

by Gamaliel Bradford

II

The supreme means for keeping theory on a basis of fact is of course unfailing, persistent, ever-varied experiment. In the preceding chapter we have seen observation lead naturally to experiment; but experiment is observation guided, directed, and illuminated by theory. And assuredly no scientist ever had the love and the habit of experiment more firmly fixed than Darwin. The explanation of phenomena was all very well in its place, essential, absorbing, but he would have agreed absolutely with Aristotle as to the proper ordering of the process: ‘After this we shall pass on to the discussion of causes. For to do this when the investigation of the details is complete, is the proper and natural method, and that whereby the subject and the premises of our argument will afterwards be rendered plain.’[462] The fascination of experiment in itself was endless and almost sufficing: ‘The love of experiment was very strong in him,’ says his son, ‘and I can remember the way he would say, “I shan’t be easy till I have tried it,” as if an outside force were driving him.’[463] There was a sense of adventure about it, of discovery, and he loved to try things that seemed almost fantastic and absurd: ‘If you knew some of the experiments (if they may be so-called) which I am trying, you would have a good right to sneer, for they are so absurd even in my opinion that I dare not tell you.’[464] And more concisely and vividly: ‘I am like a gambler and love a wild experiment.’[465] The best comment on which is the excellent remark of Professor Castle: ‘Most advances in practical affairs are made by those who have the courage to attempt what others with good reason think unattainable. When such attempts have succeeded, the world simply revises its classification of things attainable and unattainable, and makes a fresh start.’[466]

The first thing in regard to experiment is conditions. There are of course rough and elementary experiments, involving only simple principles, which do not require minute care in detail. But in many cases the nicest and most delicate preparation and adjustment are indispensable to ensure reliable results. The extensive equipment of modern laboratories was not at Darwin’s command, and though he had considerable financial resources, he could not afford the unlimited outlay of commercial research. Thus, we read of one of Mr. Burbank’s trials: ‘Forty thousand blackberry and raspberry hybrids were produced and grown until the fruit matured. Then from the whole lot a single variety was chosen as the best.... All others were uprooted with their crop of ripening berries, heaped up into a pile twelve feet wide, fourteen feet high, and twenty-two feet long, and burned. Nothing remained of this expensive and lengthy experiment, except the one parent plant of the new variety.’[467] Darwin could hardly work on any such elaborate scale as this. Yet, as one turns over his vast record of experiment, one is astonished to see how thorough and painstaking was his effort to avoid accidents and to provide for disturbing contingencies. Take, for instance, as a minor but significant illustration, his account of the difficulty in carrying out the specific fertilization of certain plants: ‘In making eighteen different unions, sometimes on windy days, and pestered by bees and flies buzzing about, some few errors could hardly be avoided. One day I had to keep a third man by me all the time to prevent the bees visiting the uncovered plants, for in a few seconds’ time they might have done irreparable mischief. It was also extremely difficult to exclude minute Diptera from the net.’[468]

Another vital consideration as to experiment, is that it should be kept impersonal. In most cases, if one is to experiment fruitfully and satisfactorily, there should be some special object in view, some particular point to be rejected or confirmed. Unless you know just what you are looking for, you are apt not to see. Again and again in Darwin’s book on Orchids, as in many of the others, we read that he made investigations and got no results, simply because he did not have in mind theoretical possibilities. When he had reasoned out what ought to happen or might happen, he often found that it did. The danger of this method is obvious. When the experimenter is so desperately anxious to see something, unless he is most carefully trained and disciplined, he will see it. It is not to be supposed that Darwin always escaped this danger, but few men have been more prepared for it or more ready to allow for it than he. His confession of prejudice, his recognition of the importance of certain points in his general theory and of his unwillingness to have anything interfere with them are among his greatest charms: ‘I remember well the time when the thought of the eye made me cold all over.... The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.’[469]

We have already enlarged under observation on the essential quality of accuracy, and it may simply be added that accuracy is doubly important in all experiments for a theoretical purpose. Accuracy, complete, detailed, mathematical exactitude, was Darwin’s hobby, and the minuteness of his record constantly exemplifies it.

Also, to confirm their accuracy experiments have to be repeated. Goethe remarks with justice that it is not necessary to travel all over the world to make sure that the sky is everywhere blue,[470] and no doubt there are repetitions that are vain and superfluous. But many difficult and delicate researches have to be gone over again and again that the minutest detail may be complete; and the process may involve months of tedious delay. Darwin’s unfailing care, both to repeat and to avoid repetition, is well indicated in his son’s comment: ‘Although he would patiently go on repeating experiments where there was any good to be gained, he could not endure having to repeat an experiment which ought, if complete care had been taken, to have succeeded the first time.’[471] Here too, one cannot appreciate how immense and thorough his experimentation was without looking through such books as the ‘Animals and Plants under Domestication’ or ‘The Power of Movement in Plants.’ The endless repetition of slightly varied combinations to test a difficult or remote conclusion makes one feel how persistent and inexhaustible the patience was. And after all the years of repeated and varied research and investigation he writes the almost pathetic epilogue six months before his death: ‘I wish that I had enough strength and spirit to commence a fresh set of experiments, and publish the results, with a full recantation of my errors when convinced of them.’[429]

Finally, experiments have to be not only made, but recorded, and the accuracy, so essential with all scientific observation, is above all essential here, since the omission of a link in the record may be ruinous to the continuity of the logical chain. It is peculiarly characteristic of Darwin that he wanted the record of error and mistake as well as of success. ‘I remember,’ says his son, ‘how strongly he urged the necessity of keeping the notes of experiments which failed, and to this rule he always adhered.’[430] The value of preserving and comparing apparently insignificant and meaningless notes is sometimes brought out, as in a special case of orchids: ‘I had given up the case as hopeless, until summing up my observations, the explanation presently to be given, and subsequently proved by repeated experiments to be correct, suddenly occurred to me.’[431] Long experience of his own mistakes and failures induces extreme scepticism as to the results of others: ‘The difficulty is to know what to trust.’[352] Even when he has taken the greatest pains, the scepticism often lingers and forces him to repeat although with an identical result: ‘Notwithstanding the care taken and the number of trials made, when in the following year I looked merely at the results, without reading over my observations, I again thought that there must have been some error, and thirty-five fresh trials were made with the weakest solution; but the results were as plainly marked as before.’[353] And thus the long series of packed, closely printed volumes forms an amazing record of a life of zealous, persistent, curious experimentation from beginning to end.