Correspondence — H. M. Deeley. 333 



subject is one worth investigation. With this view most geologists 

 will agree. Such disturbances not only affect the rocks upon which 

 the boulclei'-clays rest, but are to be found, in all kinds of glacial 

 deposits as well. Roughly speaking they may be classified as follows : — 



1. Disturbances caused by tree roots. 



2. The creep of the soil down slopes. 



3. Vertical arrangement of pebbles near surface of ground. 



4. Creep of soil-cap caused by masses of consolidated snow on 

 slopes. 



5. Dragging along of all kinds of deposits by glaciers moving- 

 over them. 



6. Ploughing up of deposits by the snouts of glaciers or by stranded 

 icebergs. 



Granting that the contortions so frequently seen may have been 

 formed in the several ways enumerated above would it not be a great 

 step in advance if means could be found whereby the different kinds 

 could be distinguished ? 



1. Roots of any size seldom penetrate very deep, but they spread 

 out from the tree trunks near the surface for great distances in many 

 cases. Their effect is not to contort the surface beds, but rather 

 to destroj 7 all traces of bedding at or near the surface. 



2. Soil creep may be the cause of crumpling the surface layers 

 of the softer rocks. Such movements would form disturbances which 

 may be likened to waves, the crests and hollows of which would have 

 a trend at right angles to the slope of the surface of the ground. The 

 growth of vegetation would tend to prevent such creep, whereas the 

 presence of much snow and frost would tend to make it more marked. 



In the case of the binding of the harder sandstones and shales at the 

 surface the only agent competent to produce the effect is either neve 

 or glacier ice. 



3. Dr. Strahan has called attention to the remarkable manner in 

 which all kinds of objects on the surface tend to assume a vertical 

 position in Spitzbergen. I have noticed that iu the ease of a large 

 number of gravels which there is reason to suppose are of Interglacial 

 age, the pebbles near the surface stand on end. It would be interesting 

 to know if the peculiarity to which Dr. Strahan refers is something 

 more than skin deep. 



4. In the case of valleys containing snow banks on their sheltered 

 sides, the creep might be of the same nature as ' soil creep ' but more 

 pronounced in character. 



5. In many of our river valleys there are river gravels which 

 show signs of great disturbance. Such disturbances are never found 

 in the more low-lying deposits. Those disturbances are very marked 

 on large flat areas and could not possibly be the result of ' soil creep '. 

 They consist of plots and undulations the trend of which generally 

 points to motion down the valley and not down the slope into the 

 valley. Very frequently they extend to depths of from 8 to 10 feet, 

 and I have seen them so marked that the gravel has been folded into 

 the Keuper Marl and the marl into the gravel. To my mind the 

 disturbances could not possibly be the result of soil creep or tree roots. 

 Glacial conditions of short duration seem the most likely explanation. 



