ON THE USE OF LIME, MARL, AND SHELL-SAND. 41 



II., but more than No. I. The brown rock in all probability is 

 formed from the blue rock ; and it is to be regretted that the 

 soil does not rest upon this rock, for a decomposition of this 

 rock would furnish a very fertile soil. 



The geological disposition of the rocks in South Devon is 

 extremely interesting, and it is to be hoped that practical geolo- 

 gists like Mr. Whitley, of Truro, chemists and practical observers, 

 will combine together in their labours, which then no doubt will 

 bring to light facts valuable to the occupier of the land. 



Again, on the clays of the granite and clay-slate, lime is of the 

 greatest utility. These two formations prevail in Wales and 

 Cornwall, and hence the soils in those parts often stand in 

 need of lime. This will appear by throwing a glance at the 

 subjoined Table, in which the composition of four soils from 

 South Wales is given : 



Composition of four Soils from Wales. 



No. I. No. II. No. IIL No. IV. 



Moisture 3*93 4*94 5*93 4*57 



Organic matter and water of combination 5*23 7*65 7*53 9'30 



Oxide of iron and alumina 6*37 13*11 7*28 10*15 



Carbonate of lime .. .. .. .. .. 8*07 "93 1*10 1-30 



Insoluble silicious matters (clay and sand) 75*47 73*18 77*81 73*29 



Magnesia and alkalies (principally magnesia) *93 *19 *35 1*39 



100*00 100*00 100*00 100*00 



No. I. is a soil from Penally, 2 miles from Tenby ; it contains 

 fragments of slate and is full of bits of lime. It has evidently 

 been limed in enormous quantities, for it requires about 400 

 bushels of burned lime per acre to add 2 per cent, of lime to a 

 soil of only 6 inches in depth, and naturally the Penally soil 

 hardly contains any lime. I am informed that this soil produces 

 only middling crops, and that a large dose is required to produce 

 any effect upon it. 



The wonder to me is that lime does produce any effect at all. 

 Chemically, i. e. as a manure, it certainly cannot act on land 

 Jimed to such an extent, and it is plain that lime can only 

 act beneficially in a mechanical way, which will explain at once 

 why large doses are necessary to produce any effect. 



No. II. is a very heavy soil from Tally bont farm, in Lawhaden 

 parish, near Narbeth. It is described to me as a good soil. 



No. III. is a soil from Greenway farm, near Narbeth. It is a 

 lighter soil than No. L, and is described to me as a very good 

 soil, which rents at about 31. an acre. It is said to require but 

 little lime, and to produce excellent pasture. 



No. IV. is a poor soil from Tegfynydd in the parish of 

 Llanfalteg, county of Carmarthen. 



