- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
The distribution of coals of different rank in south Wales, and its explanation are discussed, with reference to the recent work of F. M. Trotter. Metamorphism of the coals is considered due to depth of burial rather than thrusting. On the basis of calculated metamorphic gradients, 18,000 feet is estimated as the total depth to which the four per cent anthracite was buried.