J. G. Goodchild—On Drift. 509 



Indications of such action are to be found in the slickensided 

 faces in the till to which Mr. Geikie applies the term " striated pave- 

 ments." These closely resemble the appearances presented by the 

 faces of divisional planes in any rocks near faults, the striation 

 in both cases being due to the slipping in the plane of least resist- 

 ance of one part of the rock over another under great pressure ; the 

 only difference in the two cases being that in the case of fault slicken- 

 sides, the greatest pressure was applied horizontally, and the stria- 

 tions, therefore, run in a vertical plane ; while in the till the pressure 

 being applied vertically downwai-ds, the plane of least resistance lay 

 horizontally, and the movement has consequently taken place in 

 that direction. 



But the contorted and crushed stratified beds associated with the 

 till afford the best proof of the down settling of the ice sheet. 



In these beds we often find repeated alternations of beds which 

 are little if at all disturbed, between bands of occasionally only two 

 or three inches in thickness, in which the laminee are so violently 

 puckered and contorted that the lines of deposition are often bent 

 three or four times in succession over each other within a few inches. 

 These appearances, too, seem to be almost invariably accompanied 

 by the " striated pavements," and by innumerable faults of very 

 small downthrow. 



Probably the true explanation of most of these contorted bands is 

 that they are due to the periodical settling down of the ice upon the 

 top of pliant strata, which had not had time to reach the same stage 

 of consolidation as those immediately below. They, therefore, yielded 

 readily under the pressure of the superincumbent mass of ice, pro- 

 ducing the wildest confusion of the stratification as far downwards as 

 the more easily squeezed beds extended ; but not affecting those 

 beneath to any great depth, as must inevitably have happened had 

 the puckerings been due to the impact of a great mass of floating ice 

 in the way often suggested. 



"When the ice again came to rest, the quiet deposition of the beds 

 would again go on, and the crushed, contorted, and faulted beds 

 would be again covered up "with undisturbed strata, which again in 

 their turn might be succeeded by another set of crumpled beds 

 without being themselves affected hj the causes which disturbed the 

 overlying strata. 



Sands and gravels would not exhibit these phenomena in as 

 marked a way as the accompanying laminated clays, but they also 

 bear some traces of the same irregular downward pressure. 



It was remarked above that the sand and gravel mounds, even 

 "when they have all the characteristics of eskers, are frequently seen 

 to be moulded over bosses of rock, and to spring from headlands in 

 the same way as spits of sand and gravel project seawards from 

 the middle piers of bridges over shallow rivers, and are heaped up 

 midway between the currents which come through the arches. 



In addition to this, the occasional presence of patches of till and of 

 well-glaciated boulders in the mounds — the conformity between the 

 outer form and their internal structure, and the general resemblance 



