156 



Bishop ' s Can flings . 



The presence of so large a quantity of carbonate of lime, will 

 prevent the economic use of this material for some time to come 

 until the present supplies of phosphate are so far exhausted, as to 

 raise its marketable value. 



It is to the abundance of phosphatic earths in the Chalk, that 

 much of the fertility of the soil in this district is due. There are 

 however other elements which must be taken into consideration 

 Many plants require large quantities of carbonate of lime, and it is 

 absolutely necessary to the health of some species. Thus carrots 

 contain 164 lbs. of lime in every ton ; mangel wurzel 17J lbs., and 

 turnips 55 lbs. per ton. The Chalk on the higher hills is very 

 pure, and yields but few materials capable of supporting a healthy 

 vegetation, and the corn crops in these situations are thin; but the 

 action of the rain, frosts, &c, during many ages have tended to 

 bring about, on the lower slopes of the hills, and in the vallies, 

 an admixture of materials which possesses all the inorganic elements 

 of fine fertile soil. In some localities, as for example, in the neigh- 

 bourhood of Horton and Bishop's Cannings, the soil partakes of 

 the character of a stiff clay. This has probably been derived from 

 the marly beds of the Chalk by the long continued action of rain 

 water containing carbonic acid, which has dissolved the carbonate 

 of lime, and carried it away, leaving the aluminous or clayey 

 constituents of the Chalk undissolved on the surface. The Upper 

 Green Sand too has supplied silex to the soil of many of these 

 vallies. 



Fossil remains are not very abundant in the Chalk of North 

 Wilts, except in the flints, and in the lower or junction beds. 

 A few fine and rare Ammonites have been found on Roundway 

 Hill; and in the "Fossil Shells of the Chalk," published by 

 the Palseontographical Society, at Plate x. are figures of Am- 

 monites peramplus, a very fine species from this locality. The 

 smaller figure is from Morgan's Hill. In Plate xiii. of the same 

 publication, are engravings of Ammonites catinus from Roundway, 

 of which the late Mr. Sharpe, when President of the Geological 

 Society, says, "This rare ammonite of which only two specimens 

 have been met with, is the only species yet known in the Chalk, 



