The route of Mr. Watt is described from a sketch communicated by the late Mr. Beaufoy,[57] in which the scale appears, on a reference to the original journal, to be intended for British miles. I have regarded them accordingly; whence Laby and Teembo are placed much nearer to the coast, than Dr. Wadstrom’s map represents: for it appears by the Journal, that Kissey, at the head of the river of the same name, is no more than eight journies from Teembo. Nor has the map more than 120 geographic miles between them, admitting the scale to be British miles, as I have concluded.[58]
The nearest point in Mr. Park’s route falls at 112 G. miles to the northward of the extreme point of Mr. Watt’s; and the river Gambia lay nearly midway between them. Thus, the map of Mr. Watt forms a most useful point of comparison; and adds confirmation to the report of the natives, respecting the course of the Gambia; for Mr. Park was told, that it was crossed in the way from the Falemé river, to Foota Jallo, of which Teembo is the capital.
Pisania, on the Gambia (called also Kuttijar Factory), the place of Mr. Park’s outset[59] is stated by D’Anville to be 170 G. miles above Jillifrey, by the difference of longitude; but by M. Woodville’s map, no more than 156; which answers better to the statement of the land journey; for Mr. Park was told that it was no more than 6½ journies of a messenger.[60]
Pisania then, is placed in longitude 13° 28′, according to this result; and in latitude 13° 35′ north, according to Mr. Park’s observation, by sextant.
The causes of the apparent wanderings of Mr. Park having been explained in the former part of this work, it will be no farther necessary to trace his course, than merely to explain the connection of the different parts of the data for the general construction.
Since the scale of the Map is fixed by the computed distances arising on the intervals of time employed in Mr. Park’s route, it is possible that some readers may be startled at the idea of following such an apparently vague authority. Those, however, who have been much in the habit of observing their rate of travelling, will be easily convinced that distances may be approximated; and those in particular who have been much accustomed to travel in countries, where time regulates the distance; or who have been in habits of working up geographical materials of this kind, will be the most easily convinced. It will of course be understood, that calculations of this kind can only be received from persons of judgment and experience: and also, that when opportunities of checking them, occur, they are always resorted to; after which, of course, no alternative remains, but to adopt the corrected distance.
In the present case, the rate of travelling of camels,[61] does not apply; as Mr. Park’s journey outwards was made on horseback, and his return chiefly on foot. Nor are camels, indeed, in use in that line of route. The checks to be employed, are the number of journies reported by the travelling merchants, from different points of Mr. Park’s route to Sego and Tombuctoo; and also those from the quarters of Morocco, Tunis, and Fezzan, to Tombuctoo; using as a scale, the rate arising on the route between Fezzan and Egypt, Morocco and Jarra, as the best known lines of distance. These, altogether, furnish such kind of authority as will, I trust, lead to a satisfactory conclusion; as the general coincidence is certainly very striking.
My mode of procedure has been, to calculate, in the first instance, Mr. Park’s bearings and distances, and then to correct the bearings by his observed latitudes, as far as these extend: and beyond that, I have taken his bearing by compass, and allowed the supposed quantity of variation.
The result of these calculations, together with the addition of his line of distance from Sego to Tombuctoo, was then compared with the popular report of the distance between the several stations of Woolli, Fort St. Joseph, Bambouk, and Tombuctoo. It was found that these reports did not materially differ from the aggregate distance given by Mr. Park; although they fell short of it; a difference which might naturally have been expected, and which I have ventured to alter. The difference, however, does not exceed twenty-four geographic miles; a mere trifle in African geography. The position of Tombuctoo, so obtained, differs only half a degree in latitude, and still less in longitude, from that arising from the intersection of the lines of distance from Morocco on the NW, and Fezzan on the NE: of which a particular account will be given in the sequel.
A great part of Mr. Park’s geographical memorandums are totally lost: but fortunately his bearings by compass during a great part of the way, are preserved. In other parts, he has preserved only the calculation of latitude and longitude, arising from them; which, however, of course furnish the means of obtaining the bearings, if necessary. As he omitted to take observations to determine the quantity of the variation of the compass, after he lost the means of correcting his course by observations of latitude, which was at Jarra, about midway in his route:[62] it becomes a question of some importance, what quantity to allow on those long lines of distance between Jarra and Silla; Silla and Manding.