Mr Hugh Miller on Boulder-Glaciation. 181 



downwards. The main body of the larger boulder repre- 

 sented has evidently come into a state of rest, along with the 

 lower part of the deposit. The striae on its upper part indi- 





o ^^ 







-O' ^ (-> 



CZi 



Fig. 11. 



Section indicating differential movement in gravelly Till, New Dock, 

 Sillotli. Scale about 1 inch to \\ feet. B.Cl. gravelly Till, Sd. Sand. 



cate that moving stones and clay had continued to pass over 

 it for some time afterwards, while the till was slowly gather- 

 ing around. The fractured and detached ca'p of the boulder 

 was carried on (in the direction of ice-movement), owing to 

 this continued movement of the later deposit ; and after it 

 had, in turn, ceased to move, the gravelly till had continued 

 to pass on, the stones sliding up its front slope with axes 

 adjusted parallel to it, and then turning over as if plunging 

 down with the sluggish current on the further side. The little 

 sand-bed above is one of the ordinary insertions of aqueous 

 deposit in the till, and may indicate a little contemporaneous 

 erosion by means of water, or the formation by some means 

 of a small unoccupied basin or pouch on the surface of the 

 clay. 



To satisfy inquiry as to the thickness of the fluxion layer 

 is a matter of some difficulty. But an answer may perhaps 

 be suggested by the relation of the till to its larger boulders 

 that were glaciated in situ. The large Edinburgh boulder, 

 with its fine glaciation atop, represented in Fig. 3, was 2J 

 feet high, and had been glaciated only to a depth of about 15 

 inches. It appears, therefore, that while its upper surface 

 was in direct contact with the glaciating agent, its lower 



