13° PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 1 894, 



micaceous sediment being much more general in the southern area 

 than farther north. The comparison between the mica-schists of 

 the Start region and the Devonian slates is scarcely attempted ; 

 but much stress is laid upon the analogy between the green rocks 

 of the metamorphic area and what he calls Devonian volcanics. 

 As regards the character of the metamorphosis generally, he 

 discusses certain chemical questions, not forgetting hydro thermal 

 action, and proceeds to state that with magnesia and carbonic acid 

 available from an outside source the process of metamorphism 

 seems easy. Lastly, he concludes that there is evidence in support 

 of the hypothesis that the metamorphic rocks of South Devon 

 are Lower Devonian, and of about the same age as the sandstones 

 and slates with Pleurodictyum problematicwm of the northern shore 

 of Torbay. 



The notion of the Devonian age of the Start Schists has generally 

 found favour at Torquay, and recently, as we perceive, authors 

 have so far grappled with the details that they venture to specify 

 the Lower Devonians as the beds whose metamorphism has produced 

 the rocks in question. Now, we have learnt from Mr. Ussher's 

 paper, already quoted under ' Devonian,' that the Lower Devonians 

 on the north side of the Dart are devoid of interbedded igneous 

 rocks, and that they are essentially a gritty series with some slates 

 towards the top. But it would seem that the presumed Lower 

 Devonians on the south-west side of the Dart do contain inter- 

 bedded sheets of igneous rock, and it is the supposed metamorphism 

 of these which it is thought may have given rise to the ' green 

 rocks ' of the Start. Admitting, then, for the sake of argument, 

 that a diabase might, under certain circumstances, become a 

 " felspathic green rock of gneissoid character, containing compact 

 hornblende, much fibrous hornblende, and chlorite," is there any- 

 thing like a proportionate development of the diabase-rocks of the 

 presumed Lower Devonian of the Torcross district and the ' green 

 rocks ' of the metamorphic area ? 



This question, of course, can only be answered by geologists who 

 have made the locality their special study. But apart from Lower 

 Devonian diabases, which in some districts are not by any means in 

 evidence, it would seem that the arenaceous Lower Devonians 

 in general require a considerable amount of bolstering up before 

 they could be made to yield rocks like the general type of the 

 South Devon Metamorphics. Thus, for instance, Mr. Hunt is 

 obliged to postulate an excess of micaceous sediment for the 



