i!)5 



late years, and the importance of the inquiry may be urged as a 

 reason for promoting so far as we can the investigation of our own 

 immediate neighbourhood. 



And I would remark at the outset that this investigation is 

 attended with many sources of difficulty from which some of the 

 better known coalfields of this country are altogether free. In 

 South Wales, Scotland, and a large portion of England we find the 

 coal measures outcropping at the surface in regular succession, and 

 it only requires a careful geological survey to map their outlines 

 correctly. But in a district like Somersetshire a new difficulty 

 presents itself. We there find the carboniferous strata extensively 

 covered up by many newer formations, and it is only at a few 

 points widely separated from each other, where the more recent 

 strata have been denuded, that we are enabled to examine the coal 

 formation on the surface. 



The Map of the Ordnance Survey to which I would direct your 

 notice shows very correctly those portions of the coal measures 

 which are actually exposed, but it must be obvious from what I have 

 stated that any ordinary geological map, however good and accurate, 

 can convey but an imperfect impression of the extent of this 

 formation, and it is only by constructing a geological map leaving 

 out the covering of a more recent strata that we get any 

 adequate idea of its vast area and importance. The construction 

 of such a map however involves considerations of the gravest 

 kind. It requires us to recall the condition of things over a 

 large portion of the South of England at a very early period 

 of its unwritten history. It requires us to realize the outline 

 of that great basin in which the Coal meastires were originally 

 deposited, of the disturbing forces by which it was afterwards torn 

 asunder, and of those denuding agencies which for ages must have 

 been in operation, smoothing off all inequalities, and over large 

 tracts of country washing the formation entirely away. In short, 

 we require to construct a map of this neighbourhood, as it must 

 have appeared after the coal measures had been successively de- 

 posited, broken up, and denuded, and before the first coating of 

 Conglomerate had been deposited on their surface at the bottom of 

 the Triassic sea. 



