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.

You do not currently have access to this article.