Again, between Fort St. Joseph and Tombuctoo, M. D’Anville (Mem. Insc. Vol. xxvi. p. 73.) allows 240 French leagues. These are rated at 2,64 G. miles, or 23¾ to a degree, on his scale; consequently there results a distance of 634 G. miles. M. Lalande (Afrique, p. 23.) allows 250 leagues, which give about 660 miles. Ben Ali went from St. Joseph to Tombuctoo, by way of Tisheet and Aroan, in forty-eight days. The detour may be taken at eight days more than the direct road (for Mr. Park furnishes the positions of Tisheet and Aroan very satisfactorily), whence 40 remain, which at 16,3, produce 652 miles.
Lastly, although the following be a very vague kind of computation, it may not altogether be useless. Major Houghton’s guide undertook to carry him to Tombuctoo, from Ferbanna in Bambouk, and to return again in ninety days. Ferbanna is much about the same distance, as St. Joseph, from Tombuctoo. Perhaps no more than ten days can well be allowed for rest and refreshment, and then forty days will be the length of the journey.
The mean of the three first reports, is about 649: and on the Map, the space between St. Joseph and Tombuctoo, according to Mr. Park’s result, is 667, or 18 more.
There is then, a difference of 31 only, on the accounts between Woolli and Sego: 18, between St. Joseph and Tombuctoo; both pointing to an excess, on the part of our traveller. I am however far from offering these results, on the ground of inducing a belief that such small differences can be ascertained by such coarse materials; but rather to shew that in the general scope of the authorities, there was more of coincidence, than of disagreement, if the circumstances are rightly appreciated.
As it appears, however, that Mr. Park and Major Houghton formed different estimates of the distance between Medina and the river Falemé; and that the former exceeds by about 36 miles; and moreover, that on Mr. Park’s return by the southern route, he found by the number and scale of his journies, that he had allowed too great an extent to the space between the rivers Falemé and Gambia; I say, it clearly appears that an excess may be admitted in this part. It may be added, that, according to the report of the African travellers, at Pisania, concerning the arrangement of the journies, there is an excess on the west of Kasson; whilst the space on the east of it, agrees pretty well. Or, strictly speaking, perhaps the space is a little under-rated on the east, and much over-rated on the west. If the mean of the differences between Pisania and Tombuctoo, Fort St. Joseph and Tombuctoo, 31, and 18, that is, 24 miles be taken off, the result will be satisfactory; as it agrees pretty well with the excess found in the southern route, on Mr. Park’s return.
This naturally leads me to the discussion of the position of Fort St. Joseph, as a point connecting the upper and lower part of the Senegal river: or in other words, the routes of the French, below, with those of the English, in the interior of the country.
The French report concerning this position also points to an excess of distance from the westward; even more than that arising from the difference between Mr. Park’s reckoning and the reports of the merchants; for it amounts to about 37 miles.
Could it be ascertained that a measured survey of the Senegal river, to the height of Fort St. Joseph, had been taken, as Labat says (Vol. ii. p. 157.) was actually done, by the order of the Sieur Brüe, this would settle the matter at once. But cursory surveys have so often been called actual and measured ones, that one must be in possession of better authority, before the survey of the Senegal river can be relied on, as an absolute measure of distance. Nor is there, in the list of places in the Con. de Temps, any intimation of the longitude of St. Joseph by triangles, or measurement. Here follows a statement of the means used in fixing the position of this place.
M. D’Anville, in his map of the Senegal and Gambia rivers (1751) places St. Joseph 7° 44′ east of Ferro, which being in 17° 37′ west of Greenwich, Fort St. Joseph should be in 9° 53′. This is 32′ to the west of the position arising on Mr. Park’s route; which gives 9° 21′. But M. D’Anville supposes a difference of longitude of 6° 9′ 15″ only, between Fort St. Louis, at the mouth of the Senegal river, and Fort St. Joseph: and as I have followed M. Fleurieu’s ideas in placing St. Louis in 16° 8′ longitude, St. Joseph of course falls in 9° 59′, rejecting the seconds; making a difference of 37 G. miles, or 38 min. from Mr. Park; that is, 13 miles more than the mean of the differences between the authorities for the position of Tombuctoo.[79]
It is obvious, that as neither St. Louis nor Jillifrey, are exactly determined, in respect of Cape Verd, or of each other, it would be idle to attempt a critical adjustment of them; and therefore I have adopted the position arising from Mr. Park’s route, corrected by 24 miles, or 25 min. of longitude, more to the west; so that Fort St. Joseph stands in the map in lon. 9° 46′, lat. 14° 34′.