In July, 1804, the ardent and irrepressible Scot wrote from Prior’s Lynn, near Longtown, to a friend, Mr. William Kier, of Milholm, that the river “Enzaddi” was frequented by Portuguese, who found the stream still as large as near the mouth, after ascending 600 miles.  It is useful to observe how these distances are obtained.  The slave-touters for the Liverpool and other dealers used, we are told, to march one month up country, and take two to return.  Thirty days multiplied by twenty miles per diem give 600 miles.  I need hardly point out that upon such a mission the buyer would be much more likely to travel 60 miles than 600 in a single month, and I believe that the natives of the lower river never went beyond Nsundi, or 215 indirect miles from Point Padrao.

With truly national tenacity and plausibility Perfervidum Ingenium contended that the Congo or Zaire was the Nigerian debouchure.  Major Rennell, who had disproved the connection of the Niger and the Egyptian Nile by Bruce’s barometric measurements on the course of the mountain-girt Bahr el Azrak, and by Brown’s altitudes at Darfur, condemned the bold theory for the best of reasons.

Mungo Park, after a brief coldness and coquetting with it, hotly adopted to the fullest extent the wild scheme.  Before leaving England (Oct. 4, 1804), he addressed a memoir to Lord Camden, explaining the causes of his conversion.  It is curious to note his confusion of “Zad,” his belief that the “Congo waters are at all seasons thick and muddy,” and his conviction that “the annual flood,” which he considered perpetual, “commences before the rains fall south of the equator.”  The latter is to a certain extent true; the real reason will presently be given.  Infected by the enthusiasm of his brother Scot, he adds, “Considered in a commercial point of view, it is second only to the discovery of the Cape of Good Hope; and, in a geographical point of view, it is certainly the greatest discovery that remains to be made in this world.”

Thereupon the traveller set out for the upper Niger with the conviction that he would emerge by the Congo, and return to England via the West Indies.  From the fragments of his Journal, and his letters to Lord Camden, to Sir Joseph Banks, and to his wife, it is evident that at San-sanding he had modified his theories, and that he was gradually learning the truth.  To the former he writes, “I am more and more inclined to think that it (the Niger) can end nowhere but in the sea;” and presently a guide, who had won his confidence, assured him that the river, after passing Kashna, runs directly to the right hand, or south, which would throw it into the Gulf of Guinea.