1845.] SMITH ON SCOTCH BOULDERS. 35 



in like manner, if the striae upon boulders are only found upon their 

 exposed surfaces, we may draw the same conclusion. 



On my last visit to Scotland, I observed on the shore of the Gare 

 Loch, about twenty -five miles from Glasgow, two boulders of con- 

 siderable magnitude half-buried in the till, with their upper surfaces 

 scratched. They were near enough to enable me to observe that 

 the striae were perfectly parallel, and in the same direction in both 

 stones; and near the foot of the Campsie range of hills, I observed 

 the same phaenomenon on the exposed surface of a trap rock. The 

 direction was the same in all the three cases, viz. from the north 

 of west to the south of east. This coincidence can scarcely be acci- 

 dental, particularly as it agrees with the observations of others. 



Colonel Imrie, in his account of the geology of the Campsie Hills *, 

 notices the striated surface of the trap rocks, and their direction from 

 west to east, " except where turns in vales had partially influenced the 

 course of the current." He also notices that some of the boulders 

 had scratched surfaces, in a position which indicated they had come 

 from the west. Mr. David Milne, in his paper on the Lothian coal- 

 field, in the * Transactions of the Royal Society of Edinburgh f,' 

 states, respecting the boulders of the till in that district, " Though 

 these boulders are generally smooth, some of them have ruts or 

 scratches on their upper sides, which have been apparently pro- 

 duced by the passage over them of harder bodies. I have more par- 

 ticularly observed these scratches on blocks of limestone, sandstone 

 and greenstone. It is an object of some importance to ascertain the 

 direction of these ruts, but it is in very few places in the district 

 where this can be ascertained. The direction of the ruts can be 

 very distinctly seen along the shore at Joppa, near Portobello, and 

 at Seafield, near Leith. They appear at both places between west 

 and west-south-west by compass, but the most general direction is 

 west-half-south. A great many boulders have lately been dug out 

 of this deposit in the excavations for the Newhaven and Edinburgh 

 railway ; the direction of the scratches upon them is west-half- 

 north." 



I have never observed any furrowed surfaces below the till J ; on 

 the contrary, whenever I have seen it in contact with the subjacent 

 rock, it exhibits marks of violent action, fracture and denudation. 

 Mr. John Craig of Glasgow, whose pursuits as a mineral surveyor 

 render him familiar with this, informs me that he has observed the 

 same thing. But if the mode of deposition has been a violent one, 

 the cause must have been a transient one, otherwise the smaller 

 broken fragments would in all cases have been removed ; but the 

 contrary is the case ; by far the greatest number of fragments are 

 those of the subjacent rock, more or less rounded according to the 

 distances from which they have been brought. 



* Memoirs of the Wernerian Society, vol. ii. p. 35. 



t Vol. xiv. p. 310. 



t There is a furrowed, scratched and polished surface of the sandstone below the 

 till at the great stone-quarries of Craig Leith, of a part of which plaster casts were 

 taken by Captain Basil Hall. [Note by Referee. — Ed.] 



d2 



