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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 12, 



decay I have not noticed on Dartmoor (unless perhaps the primary 

 hollows of the rock basins have been caused by it), but the con- 

 verse 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 sphe- 

 roidal masses are still in situ. By the side of the Moreton and 

 South Devon Railway, north of Casley Cutting, there are three dis- 

 tinct 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 iMStleigh Station, Moreton ffanvpstead Railway, 



■s%c^^^ 



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, Willist^ne 



