It was originally intended to compose a full memoir on the subject of
the construction of the maps showing Dr. Barth’s travels and researches;
but the preparation of the drawings themselves has, up to the last
moment, occupied so much time that, in order not still further to delay
the publication of these volumes, an apology only for a memoir can be
offered. Besides, all the native information and the itineraries, which
form the substance of so considerable a portion of the two general maps,
have been given at full length in the Appendices to the five volumes. It
was also felt that, better than all the most elaborate disquisitions and
discussions that could be advanced in such a memoir, will be the test
applied to the maps by the Niger Expeditions, which for a period of five
years are to proceed both up the Kwára and the Bénuwé by means of
steamboats, commanded by experienced naval officers, who will set at
rest the true positions of such of Dr. Barth’s points as they may be
able to reach. The first expedition which was sent out to follow up Dr.
Barth’s discoveries, namely the expedition up the Bénuwé in 1854,
commanded by Dr. Baikie, did not, it is true, reach the point where Dr.
Barth crossed that river in 1851[131]; but a second expedition will, no
doubt, penetrate further. Meanwhile, the present expedition up the Kwára
will, it is hoped, reach Say during the present year, and, by fixing the
position of that place accurately, will offer an important point of
comparison with the results of Dr. Barth’s labours.
After the foregoing remarks, it must at once be distinctly stated that
Dr. Barth himself has made no astronomical observations either of
latitude or longitude. The best established of Dr. Vogel’s positions,
therefore, were made use of in constructing the maps, and consequently
they form the basis of most of the routes connected with Múrzuk, Kúkawa,
Zínder, and Yákoba. Beyond these points the routes were almost wholly
laid down from dead reckoning, with the exception of those from Tripoli
to Múrzuk, _viâ_ Mizda, and from Múrzuk to Ghát and Aïr, where Dr.
Overweg’s observations of latitude were made available, as well as the
only observation of longitude that could be made out from the
fragmentary and torn remains of his papers, namely, that of the island
of Belárigo in Lake Tsád.[132] It will be seen, therefore, that by far
the greater portion of the countries over which Dr. Barth’s labours
extend, was laid down either from dead reckoning or from computations of
native routes and native information. Thus the whole route from Zínder
to Timbúktu, for example, a distance by Dr. Barth’s travelling lines of
upwards of 1200 English miles, had to be laid down solely from dead
reckoning taken from a very accurately kept journal; and the magnetic
variation had to be guessed at. Yet, despite of these shortcomings, the
writer hopes that in the construction of these maps, in several of which
he was greatly assisted by the original maps laid down by the traveller
himself, he has not departed very widely from the truth; and he looks
confidently forward to their being tested by the Niger expeditions.
A great deal has been said of late on astronomical observations in
connection with African exploration, and it has—in some instances—been
represented as if only those travels and explorations which were based
on such observations were valuable, while all others were of no value.
Assertions made thus indiscriminately are most objectionable, as a
careful noting of the bearings and distances of each day’s journey, such
as Dr. Barth has made, is far preferable to many astronomical
observations which cannot be implicitly relied on; it is only the
accurate astronomical observations which deserve to be regarded as well
established points in a traveller’s route. In our own case we could
adduce many striking instances of the uncertainty of occasional
observations. Thus, although Dr. Vogel was an astronomer by profession,
fully competent to make observations with care and accuracy; yet, in the
construction of Dr. Barth’s own routes, south, south-east, and east from
Kúkawa to Ádamáwa, Músgu, and Bagírmi, we saw good reason to reject all
Dr. Vogel’s positions bearing upon these routes, as Ujé, Díkowa, Dilhé,
Wáza, Kadé (Ádishén), &c. &c., and to prefer simply Dr. Barth’s
itineraries of dead reckoning.
NOTE by Dr. Barth.—In constructing the western sheet of the general
maps, no notice has been taken of the fact of Major Laing having entered
the desert of Tanezrúfet in 23° 56′ N. (_Quarterly Review_, 1828, vol.
xxxviii. p. 101.) But we do not know whether Laing proceeded by way of
Inzíze or by some other route. It is, however, not improbable that
Aúlef, the starting point of those routes, lies about twenty miles
further south.
The identification of Bot-hadíye with Bakel on the Senegal, is not quite
certain; but at all events it is a place at no great distance to the
N.W. of it.
[Footnote 131: The information Dr. Barth was able to collect with
reference to the lower part of the Bénuwé, as far as subsequently
surveyed by Dr. Baikie, was rather meagre; yet even with regard to those
few data, provisionally as they were laid down from Dr. Barth’s original
map in A. Petermann’s “Account of the progress of the Expedition to
Central Africa, London, 1854,” Dr. Baikie acknowledges the service that
map proved to him, and records his testimony both as to the amount and
general correctness of the information it contains. (See Dr. Baikie’s
“Narrative of an Exploring Voyage in 1854,” p. 446.)]
[Footnote 132: The cardinal points of the maps where astronomical
observations had been made by Dr. Vogel, besides Tripoli, are the
following:
Longitude E. Latitude N.