The reluctance he manifests to entertain suppositions, possibilities regarding the nature, form, configuration of concrete immutable matter like the earth, arises from the fact, that a man who commits himself to theories about such an untheoretical subject as Central Africa is deterred from bestirring himself to prove them by the test of exploration. His opinion of such a man is, that he unfits himself for his duty, that he is very likely to become a slave to theory--a voluptuous fancy, which would master him. It is his firm belief, that a man who rests his sole knowledge of the geography of Africa on theory, deserves to be discredited. It has been the fear of being discredited and criticised and so made to appear before the world as a man who spent so many valuable years in Africa for the sake of burdening the geographical mind with theory that has detained him so long in Africa, doing his utmost to test the value of the main theory which clung to him, and would cling to him until he proved or disproved it. This main theory is his belief that in the broad and mighty Lualaba he has discovered the head waters of the Nile. His grounds for believing this are of such nature and weight as to compel him to despise the warning that years are advancing on him, and his former iron constitution is failing. He believes his speculations on this point will be verified; he believes he is strong enough to pursue his explorations until he can return to his country, with the announcement that the Lualaba is none other than the Nile. On discovering that the insignificant stream called the Chambezi, which rises between 10 degrees S. and 12 degrees S., flowed westerly, and then northerly through several lakes, now under the names of the Chambezi, then as the Luapula, and then as the Lualaba, and that it still continued its flow towards the north for over 7 degrees, Livingstone became firmly of the opinion that the river whose current he followed was the Egyptian Nile. Failing at lat. 4 degrees S. to pursue his explorations further without additional supplies, he determined to return to Ujiji to obtain them. And now, having obtained them, he intends to return to the point where he left off work. He means to follow that great river until it is firmly established what name shall eventually be given the noble water-way whose course he has followed through so many sick toilings and difficulties. To all entreaties to come home, to all the glowing temptations which home and innumerable friends offer, he returns the determined answer:-- "No; not until my work is ended."