Mackintosh — RaUtvay Geology in Devon. 397 



Cuttings through Granite — Beady-made Boulders. — In the two cuttings 

 south of Lustleigh station, the rock consists of irregular masses of 

 rather hard granite apparently imbedded in very soft granite stained 

 with iron, and more or less laminated (foliated ?). Here and there 

 angular blocks, or groups of angular blocks, are surrounded by a 

 matrix of loose-grained granite. In one place a dyke of trap, or 

 altered slate, rises up through the granite. In the cuttings north 

 of Lustleigh station, the granite consists of hard masses of approxi- 

 mately spheroidal shape, with soft granite intervening (PL XVIII. 

 Fig. 5). The loose texture of the great mass of the granite may be 

 increased by atmospheric influence ; but as it occurs at considerable 

 depths from the surface in fresh excavations, it must be partly, if 

 not mainly, regarded as the original state of the rock. It would, 

 indeed, be more in accordance with the appearances presented, to 

 regard this loose and soft material more as a half-formed than a dis- 

 integTated granite. At intervals the spheroidal masses lie as if they 

 had been imbedded, though they are really the effect of some process 

 akin to segregation. They have a hard, well-defined, and permanent 

 surface. The concentric layers or shells, which are sometimes in con- 

 tact with these masses, exfoliate only to a certain depth, and appear 

 to be rather hardened parts of the neighbouring matrix than the 

 outer structure of the masses themselves, though this may be in 

 appearance only. The matrix can be easily removed with the end of 

 an umbrella, leaving a large round boulder. Such boulders, how- 

 over, must be regarded as distinct from the boulders on the higher 

 grounds where the granite is hard and jointed, and where the stones 

 must have been originally cubical. While many of the latter stones 

 have evidently been transported, those around Lustleigh are princi- 

 pally in situ. The soft granite, once filling up their interspaces, could 

 not, however, have been washed away by rain, as they often rest on 

 ground where rain-water could not have acquired a transporting 

 power. The surface of the ground between these stones (some of 

 which are 15 feet in diameter) is generally smooth and not rutted, 

 and the outline of the knolls (revealed by railway cuttings) con- 

 sisting of soft granite with included hard masses, frequently presents 

 a smooth and uniformly -continuous curve — the obvious result of a 

 denudation laterally directed, and sufficiently powerful to disregard 

 the hardness and softness of materials. (See Plate XVIII. Fig. 6). 



Apparently re-assorted Granite. — On many parts of Dartmoor, not 

 only filling up hollows and covering slopes, but distributed over 

 level areas, deposits of stratified granitic detritus are not uncommon. 

 I have seen them on the road-side between the Hountor rocks and 

 Eippon Tor. But it is sometimes difficult to distinguish between 

 such deposits and soft granite in situ. At Moreton-Hampstead station 

 a large section of soft granite presents the appearance of obUque and 

 curved lamination with imbedded fragments of dark-coloured quartz ; 

 but a more minute inspection will be sufficient to convince the 

 observer that the granite is in situ, and that whatever may have been 

 the original arrangement of the crystals, the present apparent lami- 

 nation is foliation, perhaps rendered more striking by the absorption 



