VOYAGE TO ALGERIA. 125 



I wiped away the weeds and foain, 

 And brought my 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 

 M 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. 



