part 2] THE METAMOEPHOSED ROCKS OF THE START AREA. 173 



lines. But no adequate account of the raineralogical nature of 

 the peculiar Green Schists of the area was forthcoming until 

 Sir Jethro Teall and Dr. A. Harker l examined sections of the 

 rocks collected by other observers. 



In any interpretation of the structure of this tract of country, 

 the early observers were at a disadvantage, in the fact that no 

 adequate geological survey of the district had been made. The task 

 of mapping the area was undertaken by the Geological Survey, the 

 results appearing in the 1-inch map by W. A. E. Ussher, published 

 in 1898. Since that date the area has been mapped on the 6-inch 

 scale, and in 1904 Ussher's investigations appeared in the form of 

 a memoir. 2 With this memoir the long line of publications on the 

 Start rocks was completed, and no further data seem to have been 

 recorded in print. 



The results and conclusions to which Ussher was led are stated 

 in his memoir, and he appended thereto a bibliography on the 

 geology of the region, rendering it unnecessary to repeat this here. 

 The same observer dealt with the relations of the Start group of 

 rocks to the undoubted Devonian rocks on the north, but left 

 undecided the mutual relations of these groups. Beyond petro- 

 graphic descriptions of a few rocks by Sir Jethro Teall, the petrology 

 of the area, and more particularly the nature of the Green Schists, 

 which form so prominent a group in the Start stratigraphy, are but 

 lightly touched upon in the official memoir. 



The purpose of the present communication is the treatment of 

 these rocks from the petrological point of view; but it is necessary, 

 for the sake of completeness, to remark again on the stratigraphy, 

 and discuss Ussher's interpretation of the structural relations. 



II. Structure oe the District. 



Two main groups of rocks are recognized as constituting the 

 Start Point area: («) mica-schists, and (b) Green Schists. 



These rocks have a predominant east-and-west strike, and are 

 highly folded. From an examination of the coastal sections, 

 Prof. Bonney (who examined these rocks in 1884) was led to the 

 conclusion that the mica-schists formed a distinct stratigraphic 

 unit lying above the Green Schists. He was of opinion that the 

 Green Schists were basic rocks of igneous origin, but nowhere has 

 he stated definitely whether they were to be regarded as predomi- 

 nantly of tufaceous character, or as lavas or intrusions. On the 

 other hand, W. A. E. Ussher, after mapping the area on the 6-inch 

 scale, reached the conclusion that the mica-schists lay as a group 

 below the Green Schists, forming a core to anticlinal structure in 

 the Green Schists on the eastern side of the Salcombe estuary ; but, 

 in the area on the west, the coalescence of the two main bands of 



1 A. K. Hunt, Geol. Mag. 1892, pp. 341-48. 



- ' The Geology of the Countoy around Kingsbridge & Salcombe (Explan- 

 ation of Sheets 355 & 356) ' Mem. Geol. Surv. 



