170 



Proceedings of the Royal Physical Society. 



linear strips like lanes ; the most remarkable of them all re- 

 sembles one of those strips or " slips " of causeway, inclined 

 with the shore, on which it is usual to run the boats out to 

 Their slioht eastward fall is, of course, towards the 



sea. 



middle of the valley now occupied by the waters of the Forth, 

 which probably sagged a little towards the centre, as many 

 drift-filled valleys do. Besides this slight incline, two of 

 the most lane-like and pavement-like of them have, through- 

 out at least a part of their length, an even dip of two or 

 three degrees a little south of east, or at right angles to their 

 length. This dip I am unable to account for.^ 



The boulder-clay which underlies and originally enclosed 

 these boulder-pavements is of a remarkably fine and well- 

 kneaded kind, strongly clayey in its matrix, and handsomely 

 varied in the stones that mottle its surface. In quality it 

 contrasts very decidedly with the pavement. In some places 



I'l/iii 





i\Ci A.0. I 



Fig. 5. 



Sketch -plan of part of Boulder-pavement (scale 1 inch to 2 feet), Fillyside, 

 near Edinburgh. The arrow denotes direction of ice-movement. Note. — The 

 interspaces between the stones were occupied by the debris and litter of the 

 sea-shore. 



where the pavement is torn up, the till shows from under it 

 nearly as distinct as the bed of concrete under the causeway 



1 Mr B. N. Peach suggests to me that this slope may be due to their posi- 

 tion, towards one side, in the interior of a drum, or drift-ridge, now removed 

 by breaker action. This, a priori, is extremely likely. But so far as I have 

 observed, most of the single striated boulders on the coast have a similar tilt. 

 Drums are bilateral. Why do these slope all one way ? 



