236 



On the Silica Strata of the Lower Chalk. 



while the silica rock moulders away, leaving the terraces above 

 in bold relief. This simple cause adds greatly to the beauty of 

 this most beautiful part of the Isle of Wight. 



The green marl bed above, which is the upper member of the 

 upper greensand, is here from 8 to 10 feet thick. Altogether, 

 therefore, the stratum, where we examined it, may be con- 

 sidered about 170 feet in thickness. 



Section from the Isle of Wight. 



No. 



Silica. 



Carbonate 

 of Lime, 



1 



3-11 



1-34 



2 



1-71 



66-00 



3 



2-82 



5*80 



4 



3-20 



14-04 



5 



5-94 



12-5 + 



6 



9-64 



8-75 



7 



8'56 



12-50 



8 



4-84 



8-30 



Our readers will perceive, by comparing the analyses of this 

 section with those of Farnham, &c., that the silica strata of the 

 lower chalk in the Isle of Wight are not likely to furnish an 

 adequate source of soluble silica either for manufacturing or 

 agricultural purposes. We believe that the deposit in the Isle 

 of Wight has been subsequently altered by volcanic heat. 



The agricultural properties of this silica rock have never re- 

 ceived much attention until the present inquiry. It is, however, 

 a well-recognised fact that the " malm " districts have long been 

 celebrated for growing fine crops of wheat, both as regards quality 

 and quantity. Mr. Paine has grown enormously large crops of the 

 best white wheat on this soil when in a high state of cultivation, and 

 they have been remarkable for the stiffness of the straw. Until 

 recent improvements in wheat-growing were more generally prac- 

 tised, the malm soil of Hampshire was highly esteemed for its seed 

 wheat, and a very extensive district was supplied with seed from 

 this source ; thereby evincing that, without the aid of artificial 

 appliances, many parts of these soils give excellent crops. Since 

 we became acquainted with the peculiar properties of this rock we 

 have made diligent inquiries of the farmers upon the " malm " 

 soils, and they invariably agree in their testimony that the appli- 

 cation of lime once in about ten years, at the rate of a bushel to the 

 rod, or 160 bushels to the acre, is of most essential benefit — not 

 only in the increase of their crops, but more especially in stiffen- 

 ing the straw of the cereals, and in improving the quality of the 

 corn and increasing the weight per bushel. Lime has been, and 

 still is, extensively used in these parts ; and, as stated by all the 

 farmers, with about the same apparent advantage on the gault as 

 on the silica rock. On the other hand, bones have been tried again 

 and again on these soils with no perceptible profit to the crops, 



