332 Proceedings of the British Association for 1850. 



hundred feet high. It must explain how, in such a valley as 

 that of the Forth, there could be an ice-torrent of undeviat- 

 ing flow for many miles, and deep enough to envelope hills 

 many hundred feet high. 



Mr H. Miller read a communication on peculiar scratched 

 pebbles and fossil specimens from the boulder clay in Caith- 

 ness. 



Mr Miller, when examining, a good many years ago, the 

 boulder clay of Ross and Cromarty, in the vain hope, as it 

 proved, of finding in it organic remains belonging to it- 

 self, was struck by a peculiarity in the dressing of the 

 smaller pebbles which he had not seen described or ad- 

 verted to by any writer on the subject. He was aware 

 that many of the larger boulders which it contains are 

 scratched and polished like the rocks on which it rests, but 

 he was not prepared to find the smaller pebbles scratched, 

 and not less deeply than the large ones, in every case in 

 which they were not of too coarse a grain to retain the 

 markings, or of too hard a quality to receive them ori- 

 ginally. If of limestone, or of a coherent shale, or of a 

 close, finely-grained sandstone, or of a yielding trap, they 

 are scratched and polished — invariably on one, most com- 

 monly on both their sides ; and it is a noticeable circum- 

 stance, that the lines of the scratchings occur, in at least 

 four cases out of every five, in the lines of their longer axes. 

 Though in many cases, as on the western coasts of the main- 

 land of Scotland, — in the islands of Skye and Rum, with 

 several of the other Hebrides, — in Sutherlandshire, and in 

 various localities in the neighbourhood of Edinburgh, he had 

 found the scratched and polished surfaces dissociated from 

 the boulder clay, in no instance had he ever found the 

 boulder clay, if not, as in the case of our common brick 

 clays, a re-formation — dissociated from the scratchings and 

 polishings. Now, from these data the inference seems un- 

 avoidable, first, that the rock on which the clay rests was 

 scratched and polished either at the time when it was re- 

 ceiving its first coating of the clay, or so immediately before, 

 that the markings were not in the slightest degree eff^aced 

 when it was covered up ; and, second, as the pebbles in the 



