The geographical question of the watershed had now to be grappled with.  It is natural to ask whether this question was of sufficient importance to engage his main energies, and justify the incalculable sacrifices undergone by him during the remaining six years of his life.  First of all, we must remember, it was not his own scheme—­it was pressed on him by Sir Roderick Murchison and the Geographical Society; and it may perhaps be doubted whether, had he foreseen the cost of the enterprise, he would have deemed the object worthy of the price.  But ever and anon, he seemed to be close on what he was searching for, and certain to secure it by just a little further effort; while as often, like the cup of Tantalus, it was snatched from his grasp.  Moreover, during a life-time of splendid self-discipline, he had been training himself to keep his promises, and to complete his tasks; nor could he in any way see it his duty to break the one or leave the other unfinished.  He had undertaken to the Geographical Society to solve that problem, and he would do it if it could be done.  Wherever he went he had always some opportunity to make known the father-hood of God and his love in Christ, although the seed he sowed seemed seldom to take root.  Then he was gathering fresh information on the state of the country and the habits of the people.  He was especially gathering information on the accursed slave-trade.

This question of the watershed, too, had fascinated his mind, for he had a strong impression that the real sources of the Nile were far higher than any previous traveler had supposed—­far higher than Lake Victoria Nyanza, and that it would be a service to religion as well as science to discover the fountains of the stream on whose bosom, in the dawn of Hebrew history, Moses had floated in his ark of bulrushes.  A strong impression lurked in his mind that if he should only solve that old problem he would acquire such influence that new weight would be given to his pleadings for Africa; just as, at the beginning of his career, he had wished for a commanding style of composition, to be able to rouse the attention of the world to that ill-treated continent.

He was strongly disposed to think that in the account of the sources given to Herodotus by the Registrar of Minerva in the temple of Sais, that individual was not joking, as the father of history supposed.  He thought that in the watershed the two conical hills, Crophi and Mophi might be found, and the fountains between them which it was impossible to fathom; and that it might be seen that from that region there was a river flowing north to Egypt, and another flowing south to a country that might have been called Ethiopia.  But whatever might be his views or aims, it was ordained that in the wanderings of his last years he should bring within the sympathies of the Christian world many a poor tribe otherwise unknown; that he should witness sights, surpassing all he had ever seen before of the inhumanity and horrors of the slave-traffic—­sights that harrowed his inmost soul; and that when his final appeal to his countrymen on behalf of its victims came, not from, his living voice but from his tomb, it should gather from a thousand touching associations a thrilling power that would rouse the world, and finally root out the accursed thing.