VOYAGE TO ALGERIA. 165 



smote me at the time, haunts me still; for, though our 

 requisitions were moderate, this beauty ought not to be 

 at all invaded. Pendent from the roof, in their natural 

 habitat, nothing can exceed their delicate beauty; they 

 live, as it were, surrounded by organic connections. In 

 London they are curious, but not beautiful. Of gath- 

 ered shells Emerson writes: 



I wiped away the weeds and foam, 

 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 apparently 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 south- 

 ern 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 

 centre 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, sepa- 



