Clifton College Scientific Society. 29 



Artificial earthworks, too, lent their help in the process of recla- 

 mation, and there is some ground to believe that as early as the 

 Eoman occupation such dykes were constructed. Even in the 

 present day, were the barriers removed, a high spring-tide would 

 once more cover a great extent of the moor with water. Peat 

 forms now the surface covering of the plain, and it is in many 

 places not less than fom'teen or fifteen feet in thickness. The 

 evidence of an ancient sea-bottom is found in the bed of blue 

 clay which underlies the peat, and beneath it again either the 

 lias, or a kind of red marl, is occasionally seen. 



The portion of Somerset which we are now describing is rich 

 in mineral resources, and of these the most important is unques- 

 tionably coal. The enormous extent of denudation that the older 

 rocks underwent did not affect several scattered portions, which 

 were protected in the basins formed by the crumbling of those 

 rocks. So every here and there we meet with detached patches 

 of coal, fortunately spared to us, and they are found scattered 

 over an area of about 188 square miles. There is a good example 

 at Ashton, near Clifton, and many smaller beds might be named. 

 Though the southern portion of this coal-field, in particular, is 

 much covered by more recent accumulations, it is still extensively 

 worked. The Mendip range is the south-western boundary of this 

 district, and near Cheddar, so far as we have been able to learn, 

 there exist no coal-mines. But this want is compensated for by 

 the rich lead veins, which here extend through the mountain 

 limestone of the Mendips into the dolomitic conglomerate.* At 

 a very early date in history the mines of Wookey are known to 

 have been worked, and those at Cheddar have a considerable 

 antiquity. In Henry the Eighth's reign a lead tablet was dug 

 up near the former village, and, from a Latin inscription observed 

 on it, it is believed to have been afiixed to one of the trophies 

 ' erected by the Emperor Claudius to commemorate the final 

 defeat of the Cangi by the Propraetor Ostorius, a.d. 49.'-f- In the 

 Middle Ages the Mendips were famed for their lead-mines, and 

 no small portion of therevenue of the Bishops of Bath and Wells 

 accrued to them from these sources. Several remains of ancient 

 smelting-houses may be seen within a few miles of Cheddar, and, 

 though not worked with the same vigour as they once were, 

 mining operations are still carried on at some of the old workings. 

 One unpleasant result of lead extraction is the discolouring and 

 contamination of the streams in the neighbourhood, and the con- 

 sequent destruction of all fish in their waters. Calamine stone 

 (the native carbonate of the protoxide of zinc, ZnCOg) is also fre- 

 quently met with in the Mendips, and it might doubtless be 



* Lyell, 'Elements of Geology,' p. 769 {6tL eJ.) t Stevens's 'Cheddar,' p. 45. 



