PARALLEL ROADS. 



9 



have been barely covered, or, as seamen term it, 

 just lipping with the water''s edge. It is several 

 miles wide, and shaped like a delta ; its sides are 

 at many places deeply indented with ravines, which 

 enable us to see that it is composed exclusively of 

 the same water-worn materials as the roads, which, 

 on both sides, are easily traced at the same levels, 

 and in perfect conformity with those on the oppo- 

 site banks of the valley. The stones are princi- 

 pally granite and gneiss, with masses of schistus, 

 whin stone, and quartz, mixed indiscriminately, 

 and all bearing marks of having been worn by at- 

 trition under water. 



The theory which presents itself to explain 

 these appearances, supposes a lake to have been 

 formed in the valley, no matter how, and to 

 stand at the level of the highest road, till a flat 

 beach is produced by stones being washed down 

 from above. The water in the lake is next con- 

 ceived to wear away, and occasionally to break 

 down portions of the barrier across the valley; 

 this would allow the lake to discharge a part of its 

 waters into the sea, and, consequently, to lower its 

 surface to the level of the second road ; and so on 



