THE USEFULNESS OF EARTHQUAKES. 21 7 



five feet one inch thick, was dislodged from its bed, 

 and carried to a distance of from eighty to ninety 

 feet. In other parts of the Shetland Isles, where the 

 sea has encountered less solid materials, the work of 

 destruction has proceeded yet more effectively. In 

 Roeness, for example, the sea has wrought its way 

 so fiercely, that a large cavernous aperture 250 feet 

 long has been hollowed out. ' But the most sublime 

 scene,' says Dr. Hibbert, ' is where a mural pile of 

 porphyry, escaping the process of disintegration that 

 is devastating the coast, appears to have been left as 

 a sort of rampart against the inroads of the ocean. 

 The Atlantic, when provoked by wintry gales, batters 

 against it with all the force of real artillery ; and the 

 waves, in their repeated assaults, have at length forced 

 for themselves an entrance. This breach, named the 

 Grind of the Navir, is widened every winter by the 

 overwhelming surge that, finding a passage through 

 it, separates large stones from its sides, and forces 

 them to a distance of no less than 180 feet. In two 

 or three spots, the fragments which have been de- 

 tached are brought together in immense heaps, that 

 appear as an accumulation of cubical masses, the 

 product of some quarry.' 



Let us next turn to a portion of the coast-line of 

 Great Britain which is neither defended, on the one 

 hand, by barriers of rock, nor attacked, on the other, 

 by the full fury of the Atlantic currents. Along the 

 whole coast of Yorkshire, we find evidences of a con- 

 tinual process of dilapidation. Between the projecting 



