'I have always been surprised when men have advanced the view that volcanic action must have been greater when the earth was hotter, and entirely ignore the numerous indications that both subterranean and meteorological forces, even in Palaeozoic times, were of the same order of magnitude as they are now—and this I have always believed is what Lyell's teaching implies.'
I believe that Mr Wallace's expression, adopted from the mathematicians, 'the same order of magnitude,' would have met with Lyell's complete acquiescence. He was not so unwise as to suppose that, in the limited periods of human history, we must necessarily have had experience—even at Krakatoa or 'Skaptar Jokull'—of nature's greatest possible convulsions, but he fought tenaciously against any admission of 'cataclysms' that would belong to a totally different category to those of the present day.
Apart from theological objections, the most formidable obstacle to the reception of evolutionary ideas had always been the prejudice against the admission of vast duration of past geological time. It was unfortunate that, even when rational historical criticism had to a great extent neutralised the effect of Archbishop Usher's chronology, the mathematicians and physicists, assuming certain sources of heat in the earth and sun could have been the only possible ones, tried to set a limit to the time at the disposal of the geologist and biologist. Happily the discovery of radio-activity and the new sources of heat opened up by that discovery, have removed those objections, which were like a nightmare to both Geology and Biology.
Lyell used to relate the story of a man, who, from a condition of dire poverty, suddenly became the possessor of vast wealth, and when remonstrated with by friends on the inadequacy of a subscription he had offered, the poor fellow exclaimed sadly, 'Ah! you don't know how hard it is to get the chill of poverty out of one's bones.'
Geologists and biologists alike have long been the victims of this 'chill of poverty,' with respect to past time. So long as physicists insisted that one hundred millions, or forty millions, or even ten millions of years, must be the limit of geological time, it was not possible to avoid the conclusion stated by Lord Salisbury in 1894, 'Of course, if the mathematicians are right the biologists cannot have what they demand[150].' But now geologists and biologists may alike feel that the liberty with respect to space, which is granted ungrudgingly to the astronomer, is no longer withheld from them in regard to time. We can say with old Lamarck:—
'For Nature, Time is nothing. It is never a difficulty, she always has it at her disposal; and it is for her the means by which she has accomplished the greatest as well as the least results. For all the evolution of the earth and of living beings, Nature needs but three elements—Space, Time and Matter[151].'
Darwin, equally with Lyell, has suffered from a reaction following on extravagant and uninformed praise of his work. The fields in which he laboured single-handed, have yielded to hundreds of workers in many lands an abundant harvest. New doctrines and improved methods of enquiry have arisen—Mutationism, Mendelism, Weismannism, Neo-Lamarckism, Biometrics, Eugenics and what not—are being diligently exploited. But all of these vigorous growths have their real roots in Darwinism. If we study Darwin's correspondence, and the successive essays in which he embodied his views at different periods, we shall find, variation by mutation (or per saltum), the influence of environment, the question of the inheritance of acquired characters and similar problems were constantly present to Darwin's ever open mind, his views upon them changing from time to time, as fresh facts were gathered.
No one could sympathise more fully than would Darwin, were he still with us, in these various departures. He was compelled, from want of evidence, to regard variations as spontaneous, but would have heartily welcomed every attempt to discover the laws which govern them; and equally would he have delighted in researches directed to the investigation of the determining factors, controlling conditions and limits of inheritance. The man who so carefully counted and weighed his seeds in botanical experiments, could not but rejoice in the refined mathematical methods now being applied to biological problems.
Let us not 'in looking at the trees, lose sight of the wood.' Underlying all the problems, some of them very hotly discussed at the present day, there is the great central principle of Natural Selection—which if not the sole factor in evolution, is undoubtedly a very important and potent one. It is only necessary to compare the present position of the Natural History sciences with that which existed immediately before the publication of the Origin of Species, to realise the greatness of Darwin's achievement.
The fame of both Lyell and Darwin will endure, and their names will remain as closely linked as were the two men in their lives, the two devoted friends, whose remains found a meet resting-place, almost side by side, in the Abbey of Westminster. Very touching indeed was it to witness the marks of affection between these two great men; an affection which remained undiminished to the end. Lyell was twelve years senior to Darwin, and died seven years before his friend. During the last year of Lyell's life, I spent the summer with him at his home in Forfarshire. How well do I recollect the keenness with which—in spite of a near-sightedness that had increased with age almost to blindness—he still devoted himself to geological work. The 264 note-books, all carefully indexed, were in constant use, and visits were made to all the haunts of his youth, with the frequent pathetic appeal to me, 'You must lend me your eyes.' In spite of age and weakness, he would insist on clambering up the steepest hills to show me where he had found glacial markings, and would eagerly listen to my report on them. But the great delight of those days was the arrival of a letter from Darwin! Lyell was the recipient of many honours, and he declined many more, when he feared that they might interfere with the work to which he had devoted his life, but the distinction he prized most of all was that conferred on him by his life-long friend, who used to address him as 'My dear old Master,' and subscribe himself 'Your affectionate pupil.'