[p.62] ground, in valleys, with an ascent almost imperceptible to the
traveller, and the existence of which became visible only in viewing the
country from the summit of the mountains now before us. The lower hills
are seldom higher than four or five hundred feet. The lowest range above
Djidda is calcareous; but its rocks soon change into gneiss, and a
species of granite, with schorl in the place of feldspath, accompanied
by predominant masses of quartz, and some mica. This rock continues
along the road, with few variations, as far as the vicinity of Djebel
Nour, to the eastward of Mekka, where granite begins. I learned at
Mekka, that, south of Hadda, some hours distant, a mountain yields fine
marble, which served for the pavement of the great mosque. The mountains
forming the valley of Muna are composed of this red and grey granite,
and continue so from thence to this higher chain, mixed in a few places
with strata of grunstein. The lower chain of the high ridge which we
were now ascending, again, consists of grey granite; towards the middle
I found it of all colours, mixed with strata of grunstein, trappe, and
porphyry schistus, the latter much decayed: at the summit of the ridge,
red granite occurred again; its surface had been completely blackened by
the suns rays.