178 



Proceedings of the Royal Physical Society. 



axes have tlius been dragged into the line of flow. In the 

 case of some of the stones over which the pasty current had 

 passed, I even detected faint, fresh scratches running among 

 the older glacial ones, and parallel to the axis of the stone. 

 Now, this is a structure very extensively to be found in the 

 boulder-clay in situ. 



V'C 









Fig. 8. 



Fluxion -Structure in Till (natural size), Fore-shore, Fillyside, near Edin- 

 burgh. The arrow denotes the direction oif ice-movement. 



Fig. 8 represents a square inch of the horizontal plane of 

 boulder-clay on the foreshore at Fillyside. The clay and the 

 stones appear to have been in motion. The axes of the stones 

 have been turned by a common force in a general direction — 

 that of the glaciation on the boulder-pavements adjoining — 

 and from boulders a quarter of an inch in length one can 

 trace a scale of descending sizes down to minute boulders the 

 size of a very small portion of a fine pin's point. From what 

 we have just seen of the microscopic structure of the matrix, 

 there can be little doubt that if a translucent section could 

 be obtained for the microscope the grains would display a 

 structure similar to the crypto- crystalline fluxion-structure of 

 igneous rocks.^ 



1 Unfortunately the attempts to render this boulder-clay fit for slicing by 

 stiffening with Canada balsam have hitherto failed of success. The balsam 

 refused to penetrate the clay. In an excellent hand specimen which I cut 

 out (and from part of which Fig. 8 is taken), the results of fluxion-structure 

 are indicated with such nicety that Mr Peach determined the direction of ice- 

 movement without hesitation. The narrowed ends of the boulders in that 

 specimen chiefly pointed one way, like index fingers. But this is by no 

 means general. 



