Correspondence — A, R. Hunt — W. A. E. JJssher. 91 



THE DATE OF THE WOEDS " ALTEEED DEVONIAN" ON THE 

 OLD GEOLOGICAL MAP OF SOUTH DEVON. 



SiK, — Your reviewer has raised the interesting question as to 

 the date when the words " Altered Devonian " were placed on the 

 old Ordnance Survey Map of Devonshire of 1809. 



As the Devonian system was only constituted in 1839 it must 

 have been at or after that time. As De la Beche's Eeport was 

 published in the same year all his work for the Eeport was 

 completed before the term Devonian had come into use. 



I venture to suggest the possibility that the term " Altered 

 Devonian," whenever inserted, was not intended to apply to the 

 metamorphic schist series but to the rocks immediately north of 

 them, which, on the shores of Start Bay, ai'e, I believe, universally 

 admitted to be more or less altered. It seems impossible that 

 De la Beche would ever have applied the term to the metamorphic 

 schists further south, as he spared no opportunity to indicate his 

 conviction that the latter were entirely distinct. De la Beche in 

 his Report describes the different formations in successive chapters 

 according to age. The schists are described in the chapter preceding 

 that allotted to the grauwacke ; and, in the epitome of contents, the- 

 superior antiquity of the schists is indicated without the shadow 

 of doubt. A. E. Hunt. 



January 14^7j, 1905. 



GEOLOGY OF THE KINGSBEIDGE AND SALCOMBE DISTEICT. 



Sir, — In a somewhat lengthy notice of the Geological Survey 

 Memoir on the " Geology of the Country round Kingsbridge and 

 Salcombe," which appeared in your last issue (January, 1905, 

 pp. 26-37), on p. 32 we read: "The general strike of the green 

 schist zone, where the two bands coalesce to form one, would seem 

 to be approximately north-west and south-east. This direction is 

 oblique to the general strike of the Devonians on the north, and, 

 taken in conjunction with the fact that the eastern half of the 

 Metamorphic boundary consists of green schists and the western 

 half of mica-schists, seems to point to a considerable difference of 

 orientation in the two systems. Yet the author fails to trace any 

 evidence of pre-Devonian disturbance." 



The general strike of the green schist zone here referred to merely 

 applies to about a mile of country between the Moult and Marl- 

 borough (see pp. 38-39 of the Memoir), where the flattening out of 

 the great mica-schist anticline of the Start in a series of minor 

 folds allows the southern band of green schist to coalesce with the 

 northern band which all along its range is conformable in strike 

 to the general strike of the Devonian rocks. The green schists are 

 thrown out along a series of small east and west folds on the west 

 of the Salcombe estuary, and it is owing to this circumstance, and 

 not to any difference of orientation, that mica-schists are in contact 



