34 Reviews — Geological Survey — 



evidences of progressive metarDorphism detected in the Devonian 

 rocks approaching the boundary." (See antea, p. 31.) 



It is a fortunate circumstance that the numerous creeks in con- 

 nection with the Kingsbridge estuary afford sections of the boundary- 

 line, which are in some respects better than those on either coast. 

 This remark especially applies to the Southpool Creek junction- 

 section (west bank), described and illustrated on pp. 54. and 55. 

 The beds representing the Devonian portion of the junction rocks at 

 this place consist of grey slates with brown ferruginous films and 

 a local abundance of quartz veins. These beds are intersected hy 

 several small faults, whilst the schistosity dips are mostly northerly 

 at angles from 50° to 70° : they can be correlated with the slaty 

 series south of Tinsey Head (east coast) and between Beacon Point 

 and Mouthwell (west coast). The beds above described are separated 

 by a thrust with a northerly inclination "from yellowish-brown and 

 reddish-brown decomposed shales with tough masses, revealing hard 

 whitish carbonate, and definite beds of chocolate-brown rock " ; but 

 the spot where the brown rocks are in normal contact with the green 

 schists, which succeed on the south, is unfortunately obscured. 



If we are right in supposing that the ' brown rocks ' are, in the 

 main, the decomposed selvage of the green schists, and if the author's 

 section (fig. 23) and descriptions are to be relied on, we have here 

 an admirable illustration of what may prove to be the true strati- 

 graphical relations between the Metamorphic mass of the southern 

 area and the Devonian rocks of the northern area, viz., the impinging 

 of two entirely different rock systems upon each other. For such 

 a line of contact the term * fault ' is scarcely adequate, since, owing 

 to the crush and admixture of opposing materials, there has been 

 established a kind of border medley to which the author has in 

 some cases applied the term ' intermediate series.' Although this 

 intermediate series, as we might expect, varies in character at 

 different points, yet so far as the ' brown rocks ' are concerned 

 we must allow that the Metamorphic area has contributed the 

 greater part of them. This supposition is, furthermore, confirmed 

 by the facts observed in connection with the Kingsbridge estuary 

 junction-section (east side). 



We now come to an important change in the character of the 

 boundary-line on the south side, viz., the substitution of the mica- 

 schist series for the hornbleude-epidote or green schist series. West 

 of the Kingsbridge estuary the northern band of green schists is 

 split up into two groups, and the northern group is continued in 

 a westerly direction as an irregularly interplicated series of mica- 

 schist and green schist until the former wholly prevails as the 

 boundary rock. It is significant to note that henceforth, until the 

 Hope section is reached, no further signs of either green rocks or 

 decomposed brown rocks are encountered. Very little is said in 

 the memoir about the junction phenomena along the mica-schist 

 boundary. In one place the junction schists are said to be soft, 

 yellow and red in part, and very micaceous. A specimen, according 

 to Mr. Teall, is almost entirely composed of muscovite, with large 



