438 BAMBLES OF A GEOLOGIST. 



dogged perseverance of an assailant that, though baffled in 

 each single attack, ever returns to the charge, and gains by an 

 aggregation of infinitesimals, the result of the whole. From 

 the edge of a steep promontory that commands an inflection 

 of the coast, and of the wall of rock which sweeps round it, I 

 watched for a few seconds the sea, greatly heightened at the 

 time by the setting in of the flood-tide, as it broke, surge after 

 surge, against the base of the tall dark precipices ; and marked 

 how it accomplished its work of disintegration. The flag- 

 stone deposit here abounds in vertical cracks and flaws ; and 

 in the line of each of the many fissures which these form the 

 waves have opened up a cave ; so that for hundreds of yards 

 together the precipices seem as if founded on arch-divided 

 piers, and remind one of those ancient prints or drawings of 

 Old London Bridge in which a range of tall sombre build- 

 ings is represented as rising high over a line of arches ; or of 

 rows of lofty houses in those cities of southern Europe in 

 which the dwellings fronting the streets are perforated beneath 

 by lines of squat piazzas, and present above a dingy and win- 

 dowless breadth of wall. In course of time the piers attenu- 

 ate and give way ; the undermined precipices topple down, 

 parting from the solid mass behind in those vertical lines by 

 which they are traversed at nearly right angles with their line 

 of stratification; the perpendicular front which they had cover- 

 ed comes to be presented, in consequence, to the sea; its faults 

 and cracks gradually widen into caves, as those of the fallen 

 front had gradually widened at an earlier period ; in the lapse . 

 of centuries, it too, resigning its place, topples over headlong, 

 an undermined mass ; the surge dashes white and furious where 

 the dense rock had rested before ; and thus, in its slow but 

 irresistible march, the sea gains upon the land. In the pecu- 

 liar disposition and character of the prevailing strata of Ork- 

 ney, as certainly as in the power of the tides which sweep 

 athwart its coasts, and the wide extent of sea which, stretch- 



