22 The Geology of Lochruttox. 



and crops out near the surface. This rock barrier across 

 the outlet would prevent the lowering- of the stream, and 

 as the barrier and the stream are nearly at right ang-les 

 there would be no opportunity for the burn to lower its 

 channel by working- sideways. Into the upper end of the 

 Loch the feeder would be continually discharging sediment 

 from the valley above. The Loch would act as a settling- 

 pool, causing precipitation on the valley floor. 



The quantity of precipitation is governed by two 

 factors: — (i) Rate of wastage of the upper drainage area; 

 {2) erosive power of the stream upon the barrier at the foot. 

 The Silurian greywacke is extremely hard, and its surface 

 waste due to the action of weathering is of small amount; 

 l)ut all the pre-glacial torrent tracts and hollows having been 

 filled up with glacial drift, the result was that the rate of 

 wastage in that area was very great. As there was no 

 lowering of the outlet, the site of the lochan ultimately 

 iDCcame a peat moss. Its age should approximate that of 

 the Kirkconnel Moss — the twenty-five feet beach period. 



Lowering the Lade. 



As we have seen, the Lade made its escape af the lowest 

 point. This was over rock, and the consequences are a rock 

 harner and a rocky bedded stream. Had the Lade g-ot out 

 at the weak point, which would have been through the 

 village, there would have been no Loch now. 



The amount of erosion accomplished by the Lade is 

 •shown in three distinct ways : — (i) A ]o\^■ering of the bed 

 ■of the stream five or six feet, especially in the upper portion 

 next the Loch ; (2) a gradual recession of the waterfall up 

 the stream towards the Loch ; (3) a travelling of the stream 

 sideways to find a lower level. 



The vertical erosion of the Lade at the Loch outlet has 

 in this instance been the determining factor in loweringf the 

 level of the water. Yevy little has been accomplished by 

 the stream in its backward movement. From the base level 

 in front of the Water Works the falls have retreated up 

 stream to the Old Mill, forming a series of small cascades. 

 A prominent band of rock at the Sawmill has been ag-ainst 



