61 



TAB. CCCXXXV. 



The Alluvial Depositions forming Soils. 



Class 2. Earths. Order 3. Mixed. 



The surface of the Earthy alluvial or vegetating Debris, so 

 admirably contrived by the laws of Nature for our agricul- 

 tural use, have scarcely been attended to by Mineralogists, 

 and in general make so small a part in their works, that they 

 would seem to be of little consequence ; and the import- 

 ance of a more accurate knowledge, and the very use of 

 them in vegetation, has even been superseded by many chi- 

 merical ideas. Nature kindly allows, and even invites us, 

 to show industry and sagacity in many instances, but we 

 must be heedful not to mistake her contrivances. 



The top figure is a representation of a very fissile rock of a 

 nature scarcely noticed : it is a variety of clayey Shale, con- 

 taining a small portion of Iron and Bitumen : it crackles in 

 the fire, and when red-hot produces a little flame. The 

 outside passes in colour from blackish to a lightish rusty 

 brown ; it splits and falls to pieces in the weather, forming 

 at its foot a soil very different from the original appearance 

 of the rock — see the representations under it. I had it from 

 Bakewell in Derbyshire, where it is considered as excellent 

 for Firs, Elms, and Fruit Trees. The Bakewell Rotten 

 Stone, lab. 240, is a curiosity in its agricultural character; 

 it is well known to produce white Clover spontaneously 

 the second year after its being formed into meadow. Oaks 

 do not thrive in it : it is a good manure for gravelly soils. 



The right hand lower figure represents a part of a red 

 rock from Beaumares in North Wales. It has very much 

 the appearance of a baked tile. The fresh soil formed from 

 this is reckoned very fertile : it forms crumbling lumps — 

 see the left hand figure — chiefly composed of Silex, Clay, 

 and Oxide of Iron. 



