Geology. 211 



26 miles in length from north to south, and 12 miles in 

 breadth from Bath to Bristol. Bath is situated on the 

 eastern edge of this Coal basin, and but few places probably 

 in England can boast of so varied and interesting a geological 

 locality ; for within an easy day's walk no less than thirteen 

 or fourteen formations can be traversed from the Mountaini 

 Limestone on the one hand, right through the series of the 

 Coal measures and the overlying Triassic and Secondary 

 formations, to the recent Post Pliocene and Alluvial deposits 

 scattered here and there through our picturesque valleys. 



As before stated, the Mendip hills appear to have played 

 a very important part in modifying the Geology of the dis- 

 trict ; for whereas to the south of that range the thickness of 

 the Mesozoic formation from the Trias to the Inferior Oolite 

 has been estimated at more than 3,000 ft. ; these same 

 beds lying to the north within the basin have been calculated 

 to attain the minimum thickness of 169 ft. The late Chas. 

 Moore considered that this variation in the thickness of these 

 deposits to the north and south of this range of hills was due 

 to the probable presence of an old land area ; the Mendips 

 having been seldom, or perhaps never, entirely submerged 

 within Rhoetic and Liassic times, and so acting as a barrier 

 to the incursion of the waters which laid down these deposits 

 so thickly to the south. Whatever may be the true reason 

 of this difference, certain it is that the Mesozoic beds are 

 abnormal in our district, forming as it were but a com- 

 paratively thin covering to the Coal Measures below, and 

 presenting but a slight obstacle to the mining engineer in 

 winning that valuable mineral for his economic purposes.. 

 This is especially the case in the Radstock area. 



Proceeding now to a more detailed description 



''nmestone"^ ot the rocks forming the varied structure of 

 our district, and beginning with the oldest 



