Two “hours” south from Musbut to Buhuruz, two days south-east from Buhuruz, the road reaches Formah, a Zaghawa well.
Two days farther east, and it arrives at Kafut, a village in a wady of the same name, which, half a day to the south, receives a tributary known as the Wady Kobay. Wady Kafut itself, some seventy miles farther north, unites with the Wady Kuttum to form the Wady Meleeat, itself a tributary of the great Wady Howar.
Mr. Boyce’s survey shows a short section of the Wady Kuttum running east and west. Mr. Sarsfield-Hall shows Kuttum on his map as a village, situated upon an unnamed wady—presumably the Wady Kuttum—of which only a short section, running north-east to south-west is shown. But farther north he shows a large unnamed wady, discharging to the north, that corresponds well with the description I was given of the Kuttum-Meleeat Wady.
Three days farther east the road ends at El Fasher.
These routes were all taken as starting from Tollab, and when plotted on the basis of a day’s journey of twenty miles in a straight line, closed with the following errors, from the positions of their termini as shown on the maps: Bidau, 95 miles 34° from the true position, on a route from Tollab of about 430 miles as plotted—in other words, with an error of about 22 per cent of the total route. Abesher, 95 miles 98° from the true position, on a route of about 680 miles, i.e. about 14 per cent of the total distance; El Fasher, 160 miles 59° from the map position, on a fifty days’ journey of 1,000 miles, or 16 per cent of this distance. Considering the nature of the material upon which the routes were mapped, this compares not unfavourably—except in the case of Bidau—with a probable error in a prismatic compass traverse of about 10 per cent.
But this data may perhaps be misleading, for Colonel Tilho—a very accurate observer and equipped with a wireless installation for getting longitude by means of the signals from the Eiffel Tower—found that Nachtigal’s positions for some of the places in Tibesti were as much as fifty miles in error; so presumably his position for Bidau is not to be greatly relied upon. Rohlfs’ positions for Tollab, and other parts of Kufara Oasis, also remain to be checked by modern and more accurate methods than were available at the time of his journey.[21]
In constructing the maps, the routes were treated first as being three separate roads, joining Tollab to Bidau, Abesher and El Fasher respectively, and were adjusted separately by the ordinary graphic method, to their respective termini. This gave three separate positions for Bushara, Asara and Tikeru. These three positions in each case were meaned and accepted as correct, and from the position of Tikeru thus found the route to Bidau was plotted afresh and adjusted to Nachtigal’s position.
The routes south to Abesher and El Fasher were again plotted from the new position thus found for Tikeru, and were again adjusted to the map positions of Abesher and El Fasher, as two separate routes running to those places from Tikeru. This gave two separate positions for Wanjunga Kebir, Bedadi, Funfun, Wayta Sogheir and Wayta Kebir.
The mean of these two positions was taken as correct, and from this mean position for Wayta Kebir, the roads to Abesher and El Fasher were plotted and finally adjusted to their termini. Many of the places on these routes were consequently adjusted five times.
Route IV. Dongola to the Howash Valley.