GFOLOGY OF THE BRISTOL COALFrELD. 119 



the Upper Silurian to the Grecnsand portion of tho Crctaceou.-? 

 period. 



An extensive natural section of nearly all, is one well known to 

 most of us, viz., that exposed by the Great Western Railway 

 from Bristol to Paddington. This grand panoramic view of more 

 than one hundred and twenty miles in length, exposes in regular 

 sequence most of the formations with which we have to do. On 

 leaving London the railway passes over the flat surface of London 

 clay, with its brick-fields here and there shewing a section of 

 drift gravel, until it reaches the undulating chalk hills of 

 Berkshire. There is abundant evidence of this portion of 

 England having been subjected to the denuding influence of an 

 open sea. The next few miles extend over the flat and damp 

 beds of the Oxford clay. On arriving at Corsham, however, the 

 character of the land surface is seen to have undergone a complete 

 and thorough change. The railway embankment reveals the 

 rocky beds of the Oolite, which mount higher and higher until 

 the shrill whistle of the engine announces that the~ train is 

 passing through Boxhill. On emerging from the tunnel the 

 beautiful scenery surrounding the city of Bath bursts into view. 

 The railway next passes over the regular beds of the Lias for ten 

 or a dozen miles, when another change takes place, and we are 

 carried through portions of the Lias and the Coal Measures, till 

 we are landed at the Great Western terminus on an extensive 

 flat of alluvial mud. A cab ride to Clifton finishes our journey, 

 the slowness of which tells the passenger that he is toiling up 

 the slopes of the Carboniferous beds which, by an ancient 

 disturbance of the earth's surface, have been uplifted to more 

 than three hundred feet above the level of the sea. "We thus 

 perceive that our journey has taken us over most of the strata 

 marked on the Map of our President which we have taken as our 

 guide. 



A close observation of our district will shew that the portion 

 of country on the east is a series of heights having an altitude of 

 six or seven hundred feet; while the western part is a 

 continuation of low, flat country not many feet above the mean 



