§ 47. RECENT SANDSTONE OF CORNWALL. 93 



hills forty feet high. This sandstone is an interesting 

 example of a recent formation, and has been described by 

 Dr. Paris, (the distinguished President of the College of 

 Physicians,) in one of the most graphic and instructive 

 essays on modern deposits that has appeared in this 

 country.* The sand has evidently been drifted from the 

 sea by hurricanes, probably at a very remote period ; it is 

 first seen in a slight, but increasing state of aggregation. 

 on several parts of the shore in the Bay of St. Ives. 

 Around the promontory of New Kaye, the sandstone 

 occurs in various degrees of induration, from that of a 

 friable aggregate, to a stone so compact, as to be broken 

 with difficulty by the hammer, and which is used in the 

 construction of buildings. Upon examining the stone 

 with a lens, it appears to be principally made up of com- 

 minuted shells ; and it is worthy of remark, that the shelly 

 particles are frequently spherical, from the previous opera- 

 tion of water ; and some portions of the rock closely 

 resemble the ancient limestone called oolite, which will 

 hereafter come under our notice. The rocks upon which 

 the sandstone reposes are clay-slate, and slaty limestone ; 

 and the water effecting their decomposition may have thus 

 obtained the iron, alumina, and other mineral matters by 

 which the loose sand has been converted into sandstone. 

 The infiltration of water thus impregnated is a common 

 and extensive cause of lapidification : at Pendean cove, 

 granitic sand is gradually hardening into breccia, by this 

 process ; and in the island of St. Mary, is becoming indu- 

 rated by the slow action of this chalybeate. 



47. Siliceous deposits. — Silex, or the earth of flint, 

 a combination of the metallic base called silicon with 

 oxygen, is a mineral, which constitutes so large a portion 

 of the rocks and strata, that it is computed to form, either 



* Appendix E. 



