154. 



classes: 1. the Trap-Rocks which penetrate transition beds ; 2. those 

 which penetrate the old red sandstone ; 3. those which penetrate 

 the coal-measures. He refers the whole to igneous action, and con- 

 siders them to be of the same age as the rocks with which they are 

 respectively associated, rocks which he readily admits to be sedi- 

 mentary, since, though composed of volcanic materials, they con- 

 tain organic remains. The igneous action he conceives has taken 

 place under water, and the finer volcanic ejections, arranged by 

 Neptunian agency, have led to the formation of volcanic sandstones. 

 His views upon this subject appear to be in exact accordance with 

 those of Mr. de la Beche. 



Treating of the relations between igneous and fossiliferous rocks, 

 Mr. de la Beche observes*, that though frequently posterior, the for- 

 mer are in many cases contemporaneous with the strata in which 

 they at present occur, appearing to have covered an inferior bed, 

 and to have been subsequently covered themselves by a tranquil 

 deposit of transported matter, as lava may flow over a sandy bottom 

 and afterwards be covered up by sand or mud. Trappean rocks, 

 he continues, are in various parts of Europe much associated with 

 the lower parts of the grauwacke series, sometimes in a manner 

 which leaves no doubt that some of them have not been included 

 among the strata after their consolidation, while others have clearly 

 forced a passage through the grauwacke and px'eviously formed 

 masses of trap. Beds of greenstone or porphyry, he says, some- 

 times fine off among the grauwacke strata, taking the character of 

 an arenaceous deposit, as if such portions constituted a deposit of 

 trappean ashes, thrown out at the same time that the trappean rock 

 itself was produced. Brent Tor, north of Tavistock, remarkably 

 exemplifies some of these appearances. 



The researches of your Vice-President in the counties of Devon 

 and Somerset have been carried on this year with increased energy. 

 Of the eight sheets of the Ordnance Map upon which he has been 

 engaged, four were published last spring, three others are com- 

 plete, the eighth is nearly complete, and an explanatory memoir with 

 sheets of sections applying to the whole are to be published before 

 our next anniversary. Let us hope that this work so admirably be- 

 gun may not be suftered to terminate here. 



Gentlemen, we had many of us an opportunity of witnessing at 

 the late Meeting of the British Association the increasing interest 

 and success with which geology is pursued in Scotland, and we 

 felt more especially grateful on that occasion to Lord Greenock 

 and the Highland Society, for the exertions which they have re- 

 cently made to unravel the structure of their native land, and more 

 especially the nature of its coal-fields. It is not my intention to 

 detail to you all the proceedings of that Society, but I must not 

 refrain from attributing mainly, if not solely, to their exertions the 

 provision which the Government have lately made for the immediate 



* Researches in Theoretical Geology, p. 384. 



