Murchisoris Silurian System. 



239 



or altered sandstone, which has been thrown up like a wall 

 between two mining districts, the one affording copper and 

 the other lead ores. 



Agricultural character of the Silurian Rocks. — The upper 

 Silurian rocks, when not covered by transported materials, 

 afford a good substratum of clay and sand, owing to the 

 jointed and fissured character of the strata ; the soil is dry, 

 the water having once passed through the thin covering of 

 earth enters the rocks, and is thus carried off from the land, 

 which notwithstanding affords good crops of barley, oats, 

 and turnips, as well as good timber. 



On the other hand, the second division of the upper Silu- 

 rian rocks, called Ludlow and Wenlock formations, being 

 soft and argillaceous, and subject to the drainage of water, 

 are comparatively cold and unmanageable, except where 

 limestone rocks afford an intermixture of calcareous matter, 

 which yields excellent crops of wheat. 



The lower Silurian rocks afford quite a different charac- 

 ter. These rocks being for the most part of a sandy structure, 

 disintegrate into short, not very productive soil ; but where 

 the quartzose conglomerates prevail, the surface is sterile. 

 The lowest portion of these rocks consisting of flags, is often, 

 as might be expected from the nature of the beds, rich and 

 productive, particularly in Carmarthenshire, although where 

 much invaded by trap rocks, as in the mining vicinities of 

 Shropshire, the soil is generally poor. 



Lowest Fossiliferous Beds. — As the series of strata extend- 

 ing from the old redstone down to the non-fossiliferous 

 slates has been until lately regarded as a single group, 

 exhibiting the remains of the earliest animals introduced 

 upon the earth, we cannot appreciate too much investi- 

 gations which are calculated to extend our views to periods 

 so remote as those which the earliest fossiliferous strata 

 refer to. Professor Jameson we believe to have been one 

 of the first observers who discovered the elements of dis- 



