130 MEETING OF THE BRITISH ASSOCIATION 



border of which rests partly in a conformable position upon the silurian sys- 

 tem, and partly upon older rocks, partly of the division No. 4. Tts southern 

 border rests on the slate rocks of Cornwall and Launceston, and on the north 

 flank of Dartmoor. From one side to the other it exhibits an extraordinary 

 succession of violent contortions, but its true place in the ascending section 

 admits of no doubt whatever. In some places it is overlaid by patches of 

 green sand, and in one part of the coast, west of Bideford, it is overlaid by 

 the conglomerates of the new red sandstone, which are seen for half a mile 

 resting unconformably on its edge. The lowest portion of this vast deposit 

 is generally thin-bedded, sometimes composed of sandstone and slate, with 

 impressions of plants — sometimes of indurated compact slate, both in an 

 earthy and crystalline state. These beds are surmounted by alternations of 

 shale and dark-coloured limestone, with a few fossils. Subordinate to these 

 beds there are, on the west side of the county, many thin veins and flakes of 

 culon and anthracite. 



On the eastern side of the county the coal is wanting, and the 

 calcareous beds are much more expanded. On the south side of the 

 great trough, the calcareous bands and dark shales are well exhi- 

 bited ; but near Oakhampton are, as above stated, mineralized by the 

 action of the granite. The higher beds of this deposit are well ex- 

 hibited on the coast west of Bideford, and consist of innumerable 

 alternations of ferruginous sandstone, flagstone, and shale, contain- 

 ing in several places concretions of ironstone, very often exhibiting 

 impressions of plants; and one extended tract of country, containing 

 at least three beds of culm or stone coal, associated with shales, con- 

 tains many plants of species not known in the true coal measures. 

 Though in a state of greater induration than the ordinary coal mea- 

 sures of England, and in most parts almost destitute of any trace of 

 coal, yet even in these respects it differs not from a great unproduc- 

 tive tract of the coal field of Pembrokeshire. Therefore, from the 

 order of super-position, from the mineral structure, from the ab- 

 sence of that slaty cleavage which characterizes the older rocks on 

 which the deposit rests, and from the specific character of its organic 

 remains, they had no hesitation in classing it with the carboniferous 

 series. 



Mr. De la Beche read a paper on the Connection of the Geologi- 

 cal Phenomena of Cornwall and Devonshire with the Mineral 

 Veins, and exhibited the splendid ordnance map of Cornwall on 

 which its geological features are marked. The elvans-, a vein of 

 granitic character, had been thrust through the upper surface of the 

 earth, through masses of greenstone, sometimes imbedding slate 

 rocks ; and it appeared that the metallic lodes had also been, in 

 like manner, protruded through the superior formations. The same 

 coincidence occurred in Blackdown ; but the veins there were desti- 

 tute of valuable materials ; whereas, in Cornwall, they were filled 

 with rich ores. From his premises, he was of opinion that the best 

 veins of metal would be found near the granitic elvan, and in cross 

 courses. In slate, no mining speculations were likely to repay 

 those who wrought in that substance. 



A discussion of much interest to mining and those who embark 

 in it, was carried on for some time by Mr. Hopkins, Mr. Fox, Mr. 



