96 Prof. Forbes on the Topography and Geology of the 



but recently fallen in a single shower. The mode in which 

 they lie is no less remarkable. The bottom of the valley is 

 covered with rocky eminences, of which the summits are not 

 only bare, but often very narrow, while their declivities are 

 always steep, and often perpendicular. Upon these rocks 

 the fragments lie just as on the more level ground, and in 

 positions so extraordinary, that it is scarcely possible to con- 

 ceive how they have remained balanced on the very verge of 

 a precipice. One weighing about 10 tons has become a rock- 

 ing stone ; another of not less than 50, stands on the narrow 

 edge of a rock an hundred feet higher than that ground which 

 must have first met it in the descent. Possibly," adds Dr 

 M., " the presence of snow at the time of the fall may assist 

 in explaining this remarkable appearance." * 



Here we have a lively description of the blocs perches^ so 

 much insisted on by De Charpentier and others in alpine 

 geology, as a conclusive evidence of the transporting power 

 of glaciers. We have a picture also of the exact appearance 

 of a tract of country invaded by a glacier, which has since 

 retreated, but left unmistakeable land-marks of its former 

 domain. 



But I should imperfectly convey the impression left on 

 my own mind on this subject, if I were to leave the Society 

 to suppose that the valley of Coruisk alone presents these 

 remarkable traces. They are reproduced in the wild corries 

 on almost all sides of the Cuchullins ; and, in fact, it was 

 not at Coruisk that I first noticed them. A remarkable dis- 

 play of this kind is seen at the foot of the precipitous Corry 

 Reaoch, on the east side of Scuir-na-Gillean, where there 

 are roches moutonnees^ deeply striated by lines radiating from 

 the Cuchullin (in a direction from Scuir-na-Gillean to Glam- 

 ich), and a wilderness of detached blocks, extending far 

 into Glen Sligachan. Again, on the north-west we have the 

 mouth of the Corry-na-Criech, which is of immense extent, 

 fringed, as it were, with a profusion of angulai* fragments 

 from the higher Ouchullin, constituting a true moraine. But 



* MacCuUoch, Description, i., p. 388. 



