260 



IV. — Notes 011 the Geology and Archceologij of Cornwall and Devon- 

 shire.— By W. Pengelly, F.E.S., F.G.S. 



Read at the Spring Meeting, May 17, 1870. 



POLITICAL G-eography frequently takes its form, in a great 

 degree at least, from Physical Gleology. Nations cut off from 

 great rivers by narrow strips of territory, are usually suspected 

 of absorptive tendencies, and of hankering after their "natural 

 boundaries " ; and 



" Mountains interposed 

 Make enemies of nations, who had else 

 Like kindred drops been mingled into one." 



Coiopefs Time-Piece. 



Geological formations, however, pay but little respect to Politi- 

 cal Geography. Whether the men on the opposite banks of the 

 Tamar choose to be represented in the British parliament by the 

 same, or by different men, the rocks on which they dwell un- 

 doubtedly represent one and the same great portion of Palaeozoic 

 antiquity. He who would understand the Geology of Cornwall 

 or Devonshire, must, instead of restricting himself to either 

 County, often make incursions into the other, and, indeed, not 

 unfrequently go much further afield. Though this truth is so 

 obvious as to require neither argument nor illustration, the most 

 important recent fact with which I am acquainted in connexion 

 with the oldest rocks of the two Counties, bears so directly on it, 

 and is of so much interest in itself, that I am tempted to introduce 

 it here, even at the risk of making the Introduction to my brief 

 paj)er of somewhat inordinate length. 



It is well known that, through the labours of Sedgwick, 

 Murchison, Lonsdale, and Godwin-Austen, the Slates, Limestones, 

 and associated rocks of Cornwall and Devonshire — the oldest 

 rocks common to the two counties — have for upwards of thirty 

 years been held to form a distinct group — termed the Devonian, — 

 and to be of the aaie of the Old Red Sandstone of Scotland and 



