COVERING ROCK WITH EARTH. 
537 
Soil below Rock. 
One of the most singular changes of natural surface effect¬ 
ed by man is that observed by Beechey and by Barth at Lin 
Tefla, and near Gebel Genftnes, in the district of Ben Gasi, in 
Northern Africa. In this region the superficial stratum origi¬ 
nally consisted of a thin sheet of rock covering a layer of fer¬ 
tile earth. This rock has been broken up, and, when not prac¬ 
ticable to find use for it in fences, fortresses, or dwellings, 
heaped together in high piles, and the soil, thus bared of its 
stony shell, has been employed for agricultural purposes.* If 
we remember that gunpowder was unknown at the period 
when these remarkable improvements were executed, and of 
course that the rock could have been broken only with the 
chisel and wedge, we must infer that land had at that time a 
very great pecuniary value, and, of course, that the province, 
though now exhausted, and almost entirely deserted by man, 
had once a dense population. 
Covering Rock with Earth . 
If man has, in some cases, broken up rock to reach produc¬ 
tive ground beneath, he has, in many other instances, covered 
bare ledges, and sometimes extensive surfaces of solid stone, 
with fruitful earth, brought from no inconsiderable distance. 
Not to speak of the Campo Santo at Pisa, filled, or at least 
coated, with earth from the Holy Land, for quite a different 
purpose, it is affirmed that the garden of the monastery of St. 
Catherine at Mount Sinai is composed of Nile mud, transport¬ 
ed on the backs of camels from the banks of that river. Par 
they and older authors state that all the productive soil of the 
Island of Malta was brought over from Sicily.f The accuracy 
* Barth, Wanderungen durch die Kdsten des Mittelmeeres , i, p. 353. 
In a note on page 380, of the same volume, Barth cites Strabo as asserting 
that a similar practice prevailed in Iapygia; but it may he questioned 
whether the epithet rpa^ela, applied by Strabo to the original surface, ne¬ 
cessarily implies that it was covered with a continuous stratum of rock, 
t Parthey, Wanderungen durch Sicilien und die Levante, i, p. 404. 
