The tract of country extending across this island, from the sea-coast of Galloway to that of Berwickshire, consists, with little interruption, of that species of rock, which has of late been most generally known by the German name of Grauwacke. But as this rock does not differ essentially from what in Cornwall is called Killas, I am disposed, in concurrence with several members of this Society, in particular with Mr Allan, who has of late been in Cornwall, and has paid particular attention to that subject, to reject the uncouth term Grauwacke, and adopt that of Killas, as being more congenial to our language.