294 p. KUTLEY ON THE SCHISTOSE 



most likely denuded together "with the upcast part of the cone; 

 •while the remainder may either be faulted beneath the present 

 surface of the ground, or may possibly be represented by a basalt 

 which occurs at the foot of Brent Tor on the northern side. 



In dealing with the preceding questions I have merely expressed 

 opinions which are based upon a fair but not very extensive series 

 of facts, all, unfortunately, which we have at our disposal at pre- 

 sent. More must be learnt concerning the lie of the beds before 

 we can speak positively upon many of the questions raised in this 

 paper. There yet remains much for geologists to w^ork out in 

 the country between the Tavy and the Tamar. In speaking of the 

 possible relation between the volcanic series of Brent Tor and that 

 of Saltash I am fully aware of the danger of basing arguments merely 

 upon lithological characters ; and I should be loth to assert, because 

 two series of rocks were identical in mineral constitution, in structure, 

 and in mode of occurrence, that they therefore belonged to the same 

 geological horizon. The broader qiiestions discussed in this paper 

 are neither to be solved by a few weeks of desultory stone-breaking, 

 nor by a life-time of speculation based upon imperfect data. 



More facts must be accumulated before we can thoroughly un- 

 derstand the structure of the Brent-Tor district. 



Discussion-. 



The Peestdent, in returning thanks to the author, stated that he 

 had met with amygdaloidal cavities, due to the giving off of gases, 

 in some of the older slaty ashes. 



Mr. Thorpe called attention to a specimen of lapilli from Brent 

 Tor, found in the joints of a limestone at Newton Abbot. He 

 thought these proved that the S.W. wind blew in Devonian times. 



Prof. Ramsay wished to ask the President where the slates with 

 amygdaloidal cavities were. 



The President said in Cumberland. 



Mr. Etheridge thought that in the area treated by the author 

 the junction between Devonian and Carboniferous (as marked in 

 the Survey Map) was brought too far south, and that these rocks 

 will prove most valuable as indicating the boundary-line here, as 

 in Cornwall. It was unfortunate that no fossils had as yet been 

 discovered in the area under notice. 



Prof. HiroHES agreed in removing the boundary-line further 

 north. He was perplexed at hearing Mr. Thorpe speak of open 

 fissures existing in Devonian times in Devonian rocks, and still to 

 be seen. He pointed out that the material was arranged vertically, 

 as in a calcareous deposit, not horizontally as if dropped into an 

 open fissure ; and he asked whether Mr. Thorpe had tested the 

 material with acid. 



Mr. Thorpe gave some explanation of the mode of occurrence. 



Prof. BoNNEY agreed that many of the rocks were lavas, but 

 doubted if crushing accounted for their foliation. A foliated structure 



