Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/374

 decay I have not noticed on Dartmoor (unless perhaps the primary hollows of the rock basins have been caused by it), but the converse takes place ; the adjoining rock decays, and spheroidal masses are left. At Furlong, near Chagford, sections of the spheroidal masses are seen in large-grained but tolerably compact granite, in the face of an old quarry ; and in the adjoining field, on a knoll where the granite is disintegrating, the upper parts of two globular masses are well shown, one highly felspathic, and in a state of decay, the other still retaining the external coating. A very fine example of a section of the same in decaying granite was, until this month (March 1869), visible by the roadside between Rushford and Chagford, but is now hidden by a wall. In these cases the spheroidal masses are still in situ. By the side of the Moreton and South Devon Railway, north of Casley Cutting, there are three distinct disk-shaped blocks of hard rock, evidently once forming parts of the same bed ; they are supported on pedestals of soft decaying granite. Almost opposite to the Lustleigh Station, on the same line, are the finest examples of spheroidal masses in situ with which I am acquainted (fig. 3) ; these have already been described by Mr. Mackintosh in the paper to which reference has already been made. As remarked by Mr. Mackintosh, it is probable that from this action many of the supposed boulders in the neighbourhood of Lustleigh

Fig. 3.- Decaying Granite, showing in situ blocks resembling Boulders, near Lustleigh Station, Moreton Hampstead Railway.

have originated, the blocks possibly not being far removed from the spots that they occupied when in situ. To this cause probably also may be ascribed the shape of various large insulated rocks found in the district where this spheroidal structure is so apparent, such as the large rocks in the Rushford Woods near Chagford, Willistone