N. to S. which is the same with the course of the river flowing through it. Thus it appears that these rallies, which are all similar to each other, are perpendicular to the mountain pIain.[1]
Leaving the hed of the river Erme to the left, about five minutes walk from Ivy-Bridge, we pass some farm houses at the bottom of a small detached hill, the name of which I did not learn, nor do I find it laid down in the common maps of the county: it is situated N.N.E. of Ivy-Bridge, and from thence to the top of the hill is about two miles and a half by the nearest road. This small hill, the only abrupt face of which is towards the south, is situated on the exterior line of the mountains of Dartmoor, on the first plain they form from the sea coast. The upper half is composed of a nick which I call a porphyritic granite,[2] and the lower part as well as the base is of grauwacke. I found the summit to be one thousand one hundred and thirty feet above the level of the sea, and the greatest height to which the grauwacke rises on its sides is six hundred and thirty-one feet.
There is on the right bank of the Erme another small hill, facing the latter, equally rounded in its outline: both have that appearance which Saussure calls moutonnée,[3] an expression in my opinion peculiarly applicable to the low granite mountains of the ci-devant Forez.
- ↑ In the Alps, the vallies are longitudinal and transverse; in Jura, they are almost all longitudinal; in the Vosges, the greater part are oblique; in the Pyrenes, they are nearly at right angles. Journal des Mines, No. 126.
- ↑ The base of this porphyritic granite is a beautiful hind of felspar of a brick-ref colour, confusedly crystallized, in which are imbedded crystals of vitreous quartz, hornblende and tender steatite of a greenish yellow. I found on the summit several adventitious blocks of amethystine quartz.
- ↑ The mountains which Saussure designates by this expression (moutonnée) are composed of an assemblage of rounded tops, covered sometimes with wood, but more frequently with shrubs or brushwood. These rounded tops being contiguous and in frequent succession, have on the great scale, the appearance of a thick fleece, or of one of those wigs which are called moutonnée, The mountains which assume that form are almost always composed of primitive rocks, or are at least steatite; mountains of limestone or slate have never that appearance. Voyages dans les Alpes, § 1061.
