In consequence of this correction, all the eastern positions, Joag, Jarra, Sego, &c. must of course recede 25 minutes to the westward of the arrangement heretofore made, on the construction of Mr. Park’s geographical materials. Hence I place
| Joag, in | 9° | 37′ | west, | instead of | 9° | 12′ |
| Jarra, in | 7 | 13 | 6 | 48 | ||
| Sego, in | 2 | 26 | 2 | 1 | ||
| Silla, in | 1 | 24 | 0 | 59 | ||
| And Tombuctoo, in | 1 | 33 | east, | 1 | 58[80] | |
I now proceed to state the reports of the distance to Tombuctoo, from the NW, N, and NE.
From Tatta[81] on the southern frontier of Morocco, 9½ journies to the SSE of the capital, (equal to 157 G. miles) the distance is 50 journies of the caravan, according to Mr. Matra.
From Mourzouk, the capital of Fezzan, (taken to be in latitude 27° 48′ and longitude 15° 3′ east, or directly south of Mesurata), 64 journies, according to the report of Ben Ali. And from Tunis, 77 journies, through Kabes and Gadamis, according to Mr. Magrah.
On the route between Mourzouk and Cairo, as well as between Morocco and Jarra, it has been already stated ([p. xxxviii]), that 16,3 and 16,25 were the mean rates: and the former was accordingly adopted between Woolli and Sego. At the same rate, the 50 days from Tatta, give 815 G. miles, and the 59½ from Morocco, 970. The 64 from Mourzouk give 1043; and the 77 from Tunis, 1255.
Now the above assumed position of Tombuctoo, falls exactly at the given distance from Morocco through Tatta; and 18 short of that from Fezzan (Mourzouk); but 61 beyond that from Tunis. The coincidence therefore of the three lines of distance from the Gambia, from Morocco and Fezzan, may be regarded as complete, since, in using the same rate nearly across the whole continent of Africa, from Cape Verd to Egypt, a difference of 18 miles only, arises. And hence, the public mind may well be satisfied at present respecting this important position. Whichsoever of the two determinations may be right, is of little consequence: but I hold it to be more prudent to adhere to that line which is the result of computation in detail, and corrected as above, than to the long lines given in the aggregate, and in which there is more risk of error. And thus I close the subject of the position of Tombuctoo; placing it in latitude 16° 30′, longitude 1° 33′ east of Greenwich.
Something, however, is proper to be said, concerning the rate of travelling adopted on the present occasion, as it differs materially from that allowed on long lines of distance, in the Proceedings of the Association, in 1790. I there allowed 16½ for a single day, but, diminished the rate according to the length of the lines of distance. It would appear that the proportion of diminution allowed, although proper enough in countries, where obstacles interpose to change the line of direction, is not applicable to that part of Africa, where the great Deserts are crossed in so straight a line, as hardly to increase the simple winding, arising on each day’s course, in any considerable degree; and that even the simple winding is less than elsewhere. And hence 16¼, or more, arises on the camel routes, on long lines of distance, across the Desert; and on the pilgrims’ routes, where it appears the camels travel with light burthens. It was through misconception of this rate, that I placed Tombuctoo, so far to the north. I am ignorant of the cause of M. D’Anville’s error.
The particulars of the geography between Silla and Tombuctoo, are copied exactly from Mr. Park’s map; and require but little elucidation. Jinné, a large town, is two short journies below Silla: and Tombuctoo, twelve still lower down. It would appear that all the journies were conceived to be short, as Mr. Park allows only 200 G. miles for the aggregate of the 14.
Two days below Jinné, the Joliba expands itself into a considerable lake, already mentioned by the name of Dibbie; from whence the river again issues in a number of streams. These unite at a lower point, and then form two large branches, which separating widely from each other, form an island near 100 miles in length, whose name being Ginbala, or Jinbala, we recognize in it, the Guinbala country of M. D’Anville; as in the northern branch of the river that bounds it, the river of Guin, mistaken by him for the original head of the Tombuctoo river (or Niger); as he also mistook the lake of Dibbie for that of the Senegal river. Such were the errors in the African geography, to the date of the African Association: one of which errors conducted the Senegal river through 500 miles of the space which is, in reality, occupied by the Niger.