70 REPORT—1846, 
only as fossils in Europe, as Leda obtusa and truncata, and Pecten Islandicus. 3, The 
observation that several rare species now living in our seas appear at a comparatively 
recent period to have been much more abundant; and the inference that they are 
now gradually dying out, which leads to the probable conjecture that many of the 
late tertiary forms became extinct within the historic period, 4, The observations 
of the existence of limited tracts, usually of considerable depth, at various points in 
the British seas, the marine inhabitants of which are much more arctic in character 
than those generally diffused through this region. 
On the Physical Character of the Table-land of Abessinia. By CHar.zs T. 
Bexe, Esq., Ph.D., F.S.A., F.R.G.S., Corresponding Member of the Geo- 
graphical Society of Paris. 
The object of this memoir is to show the true character of the high table-land of 
Abessinia, in which the numerous head-streams of the Nile have their origin. 
The opinion expressed by Professor Ritter in his Erdkunde, and generally enter- 
tained on his authority, with respect to this table-land is, that it consists of a suc- 
cession of terraces rising one above the other, the lowest being towards the Red Sea, 
and the highest being in Enérea, where the line of separation between the waters 
flowing into the Nile and those of the rivers having their course to the Indian 
Ocean is considered to exist. 
Dr. Riippell was the first to show that so far from the high land rising in ter- 
races as it recedes from the coast, its summit line is towards the coast itself, and 
that from thence it falls gradually towards the interior. And this view is entirely 
corroborated by the two vertical sections of the Abessinian plateau, from north to 
south, and from east to west, exhibited by Dr, Beke to the meeting*. These sec- 
tions show that at Halai on the summit of Mount Taranta, twenty-three geographi- 
cal miles from the Red Sea at Zilla (Adule), near Masséwah, the edge of the table- 
land has an absolute elevation of 8625 feet, which gives a rise of 1 in 16°15— 
equal to an angle of 3° 33'—to the eastern slope. On the other hand, at Khartim, 
at the junction of the White and Blue Rivers, in nearly the same latitude as Halai, 
and at a distance of 380 geographical miles from that place, the elevation of the 
Nile is 1525 feet. The fall in that direction is therefore only 1in 324, which gives 
rather more than ten minutes and a half of a degree, as the angle of the western 
slope towards the interior of the continent. Consequently, on a line along the 
fifteenth parallel of north latitude, the eastern slope of the Abessinian mountain- 
chain towards the sea is to the western counter-slope towards the Nile as 20 to 1. 
If the proportion of the two slopes, instead of being estimated on a direct east 
and west line, be calculated on one in the general direction of the courses of the 
principal rivers, namely from S.E. to N.W., the result is as follows. Khartim 
lies very nearly to the north-west of Mélka-Kuyu, the ford over the Hawash on 
the way from Tadjdrrah to Shoa, at which spot the absolute elevation of that river 
is about 2200 feet. The height of the eastern edge of the table-land on the summit 
of the Chakka mountains behind Ankdbar, the capital of Shoa—not far from the 
direct line between the two extreme points—is about 9000 feet ; and as this locality 
is thirty-eight geographical miles from Mélka-Kdyu, it gives a rise of 1 in 38°83 to 
the eastern slope—equal to an angle of 1° 41’. On the other hand, the distance 
from the summit of the Chakka to Kharttim being about 532 miles, the fall of the 
counter-slope is 1 in 429, equal to an angle of 8'. These calculations make there- 
fore the proportion of the two slopes to be as 12°6 to 1, 
In this latter instance the eastern slope is taken, not from the level of the ocean, 
but from that of the Hawash, which river is here the recipient of the waters of that 
-slope, in the same way as the Nile itself is the recipient of those of the western 
counter-slope. From the Hawash to the sea is about 200 miles, which gives a fall 
of 1 in 550, equal to an angle of six and a quarter minutes of a degree, for the low 
desert country inhabited by the Beduin Dankali tribes. 
As a whole, the table-land of Abessinia may be described as a succession of ex- 
tensive undulating plains, declining very gradually towards the west and north- 
west, and being intersected by numerous streams; which streams, after a short 
* These sections are given on the map in vol. xiv, part 1, of the Journal of the Royal 
Geographical Society. 
