COEEYS WITH OE WITHOUT LAKE-BASINS. 139 



and there is a sufficient catchment above it, the 

 hollow formed by the break, especially during wet 

 weather, will be occupied by a mountain torrent. 1 

 These carry down yearly a greater or less quantity 

 of detritus, thereby forming a bar across the 

 mouth of the coom or corry, and impounding the 

 water behind it, thus forming a lake-basin partly 

 rock and partly drift. Such bars are always more or 

 less regular, which distinguishes them from moraine 

 drift similarly placed, as in general the latter is 

 more or less irregular, unless its form has been 

 modified in outline by marine action. Furthermore, 

 meteoric bars are seldom as compact as moraine- 

 drift; consequently, it is not unusual to find lake- 

 basins, so built up, having an overground outlet only 

 in very wet weather, while at all other times the 

 surplus water percolates through the meteoric drift 

 bars. 



1 Mackintosh describes such mountain torrent-courses under the 

 Cumberland name, " Rake." 



