Note 58 — Chapter III
Reading edition
The Thames, between Maidenhead Bridge and Mortlake, (about 41 B. miles in a straight line,) has a fall of rather more than one foot eight inches in each mile. But this is a smooth part of its course: for although the Thames does not, by any means, spring from very elevated lands, it cannot be supposed to fall less than four feet in each mile, taken on its whole course. On this idea, the Niger should have a fall of more than 8000 feet, in its supposed course to the White River. But even if two feet and a half (which appears very moderate indeed) be allowed, the fall would be no less than 5625 feet, or 115 yards more than an English mile. Is it to be credited, that the bed of the White River, on the south of Darfoor, and at a point not very remote from its source, is a mile lower than the springs of the Joliba, or Niger?