64 ON ERRATIC BLOCKS. 



blocks of stone were impelled forwards to occupy 

 their present position, inasmuch as currents of water, 

 or waves of translation, adequate to the transmission 

 of such masses, must have swept before them all the 

 loose sand and gravel and earthy matters which they 

 met with in their course, and have made that part of 

 the bed of the ocean bare over which they travelled ? 

 Those blocks of stone would have, therefore, been 

 impelled forward over a rocky bottom ; and because 

 of this, their edges would have been subjected to 

 attrition, and their angular parts rounded off. 



In the island of Arran, about a mile east from 

 the village of Lamlash, I found upon the sea-shore 

 blocks of granite of several tons weight. The 

 upper part of each had its angular parts rounded 

 off; but the base of each, which rested upon the 

 level surface of a sandstone rock, was flat, as is 

 here represented. 



FIG. 17. 



