720 THE JOURNAL OF GEOLOGY. 



whole, stratified material is more abundant in valleys, and on low 

 areas adjacent to high ones, than elsewhere, but there is no hard 

 and fast topographic relation between the two types. The asso- 

 ciations of the two phases of drift are often such as to leave 

 no room to doubt the essential contemporaneity of their origin. 

 The lithological likeness of their materials leaves no room to 

 doubt that the two phases of the drift came from the same 

 general source. From these considerations we conclude that 

 the drift agent or agents must have been capable of producing 

 deposits which were sometimes stratified and sometimes unstrat- 

 ified, and that in many places the deposition must have occurred 

 under such circumstances as to allow of the frequent change 

 from the one phase of deposition to the other. 



Foliation of the unstratified drift. While the finer part of the 

 bowlder-clay — the matrix in which the bowlders are set — shows 

 no stratification, it frequently has a sort of structure which may 

 be termed foliation. Roughly speaking, it is comparable to the 

 foliation of gneiss, though of course without the crystallinity of 

 the latter, and without differentiation of its mineral constituents. 

 The foliation is always somewhat irregular, but is usually approx- 

 imately horizontal, or approximately parallel with the surface. 

 The regularity of its development is usually interrupted where it 

 comes in contact with a bowlder. The foliation lines have a 

 tendency to curve up over, and down beneath, the same, while 

 at the centre of the sides of the bowlder they are rarely devel- 

 oped. The study of this foliation structure suggests that much 

 of it is the result of pressure. In this case, the approximate 

 horizontal direction of the parting planes suggests that the pres- 

 sure was not far from vertical. In some cases the foliation is 

 such as to suggest that it is the result of a shearing movement 

 in the fine, earthy material. The position of the horizontal 

 cleavage planes suggests that the pressure inducing the shear 

 must have had a horizontal element. 



Foliation is restricted to the unstratified portion of the drift, 

 though even here it is by no means universal. It is rarely so 

 distinct as to be obtrusive, and may easily escape the observation 



