VOYAGE TO ALGERIA. 125 
1 wiped away the weeds and foam, 
And brought iny sea-born treasures home : 
But the poor, unsightly, noisome things 
Had left their beauty on the shore, 
With the sun, and the sand, and the wild uproar. 
The promontory of Gibraltar is so burrowed with caverns 
that it has been called the Hill of Caves. They are appar- 
ently related to the geologic disturbances which the rock 
has undergone. The earliest of these is the tilting of the 
once horizontal strata. Suppose a force of torsion to act 
upon the promontory at its southern extremity near 
Europa Point, and suppose the rock to be of a partially 
yielding character; such a force would twist the strata into 
screw-surfaces, the greatest amount of twisting being 
endured near the point of application of the force. Such 
a twisting the rock appears to have suffered; but instead of 
the twist fading gradually and uniformly off, in passing 
from south to north, the want of uniformity in the material 
has produced lines of dislocation where there are abrupt 
changes in the amount of twist. Thus, at the northern 
end of the rock the dip to the west is nineteen degrees; in 
the Middle Hill, it is thirty-eight degrees; in the center of 
the South hill, or Sugar Loaf, it is fifty-seven degrees. At 
the southern extremity of the Sugar Loaf the strata are 
vertical, while farther to the south they actually turn over 
and dip to the east. 
The rock is thus divided into three sections, separated 
from each other by places of dislocation, where the strata 
are much wrenched and broken. These are called the 
Northern and Southern Quebrada, from the Spanish 
" Tierra Quebrada," or broken ground. It is at these 
places that the inland caves of Gibraltar are almost ex- 
clusively found. Based on the observations of Dr. Falconer 
and himself, an excellent and most interesting account of 
these caves, and of the human remains and works of art 
which they contain, was communicated by Mr. Busk to 
the meeting of the Congress of Prehistoric Archaeology at 
Norwich, and afterward printed in the " Transactions" of 
the Congress.* Long subsequent to the operation of the 
* In this essay Mr. Busk refers to the previous labors of Mr. Smith, 
of Jordan Hill, to whom we owe most of our knowledge of the geology 
of the rock. 
