10 GEOLOGY. 



present seas, and which explain to us the greater opera- 

 tions of a former era, or show us how, in slowly-accu- 

 mulating periods, changes as great are in preparation 

 even now. The formation of beds of the remains of 

 recent testacea, Crustacea, and fishes ; the gradual indu- 

 ration of conglomerates under the sea; and the drifting 

 of sands by the wind, may all be observed in different 

 parts of our coast, and in some to a very remarkable 

 degree. The changes effected by wind-blown sands 

 have very materially altered the features of several parts 

 of the British coasts, converting tracts of fertile land 

 into deserts as sterile as those of Africa. Lyell men- 

 tions a district in the north of Cornwall, once cultivated 

 and inhabited, where the drifted sands now form hills 

 composed of minute fragments of sea-shells, several hun- 

 dred feet above the level of the sea. Here the sand 

 may in several places be found undergoing a process of 

 indjiration, and in some parts the change is so far 

 advanced that blocks are used as building-stone ; and 

 thus the geologist can trace the gradual formation of a 

 sandstone-rock. But the interest of this locality is not 

 confined to the geologist. The archaeologist will visit it 

 as the residence of one of the early missionaries, by 

 whose labours Christianity was introduced into this re- 

 mote part of Britain, and where, on the overthrow of so 

 many British Churches by the subsequent incursions of 

 an unchristian horde, the light of truth continued to 

 shine till the commencement of a happier era. Here, 

 toward the close of the fourth century, St. Piran, born 

 of noble parents, in the county of Ossory, in Ireland, 

 A.D. 352, and converted to the Christian faith in 382, 



