Much of the Origin of Species and all of the Descent of Man was founded on this method; thus in the former the conceptions of struggle took their main rise from the work of Malthus on Human Popula-tion, and of variation from domesticated animals and plants, and this is true also of Wallace. A mere glance at the divisions of The Descent of Man shows that it could never have been attempted in any other than the backward way .
Geology.
In their researches on the crust of the earth Playfair, Hutton and Lyell did not pursue them by going down a coal mine till they came to the lowest available beds and work upward from these to the highest. Though for purposes of exposi-tion a great geologist, as Sir Archibald Geikie, may expound the making of the earth from the lowest to the highest levels, and Professor Bonney tell us the Story of our Planet from beginning to end as if he had watched it unfolding, Lyell in his Principles of Geology shows how the studies of his great province began. There we have the backward reading of its story pursued by himself and other great ones, and where it led them. Commencing with the Pleistocene period and passing through Neocene and Eocene periods through the Mesozoic Era and its cretaceous, jurassic and triassic systems to the Newer Pal?ozoic Era and its Permian, carboniferous, and Devonian systems, the older Pal?ozoic Era and its Silurian Ordovician and Cambrian systems, he reaches the unknown. But before all this patient research and its record is reached he treats, as he must, of consolida-tion and altera-tion of strata, of petrifica-tion of organic remains, elevation of strata, horizontal and inclined stratifica-tion, of faulting, denuda-tion, upheaval and subsidence as they combine to remodel the earth’s crust. The title of his classical work is significant—An Attempt to Explain the Former Changes of the Earth’s Surface by Reference to Causes now in Operation (it may be noted that in 1830 they were fond of capital letters and of underlining their words). If these great men had been condemned to the sole use of the method of the annalist in his treatment of human history, that of the coal mine in geology, this great province of knowledge would never have been what it is to-day .
At this point I think it well to state that this illuminating principle of Lyell is pursued in nearly all the matters of fact and their interpreta-tion contained in the following chapters, so that from time to time I shall have to employ the verb, coined for the purpose, when I attempt to “Lyell” them on behalf of Lamarck.
Anthropology.
The anthropologist could hardly make a start with his research, if, knowing nothing of his own anatomy, physiology, customs and beliefs, he tried to interpret the physical features, habits, manners, customs and rites of an African tribe. Without such prior knowledge he would find it a profitless task to journey to the banks of the Zambesi and bring back any intelligible history of the aborigines. If he did not know the games of a European child how could he
understand the variants of them such as the writer of Savage Childhood2 expounds so well?
The Sources of Rivers .
To trace the course and source of a river is a simple task through the work of modern geographers, and such a pursuit illustrates well the two methods here considered, but it is doubtful if any river was ever traced originally from its fountain head to its mouth. The backward way of such explora-tion, from the nature of the case, has always been taken, and men have traced the more or less finished products of the lower stretches, backward, still backwards, even as in the Indus, to the still-unknown. The earliest thinkers and seekers in the plains of Bengal were familiar with much of their great sacred and composite river as it flowed into its delta. Slowly, laboriously, here a little and there a little, they learned its stupendous story. They found the plateau of Tibet in the Himalayas where the twin-sisters, Brahmaputra and Ganges were born, and saw how from the one high cradle they parted on their eastward course for a thousand miles with the mountain-chain between them, and how, coming together again, the one descending through Assam and the other flowing through the plains, reinforced by the Jumna, they united to form the Ganges-Brahmaputra. A great subject indeed for the early geographer, but one which he could only follow in the backward way. Again how well known and revered in Egypt was the Nile for thousands of years before its source in Victoria Nyanza could be traced, even though Nero might send his explorers as far as the marshes of the White Nile, and Ptolemy’s search for it might lead him to guess the riddle, and assign it to two great lakes!
Genealogy.
