Rake Vem at Det'weni Lead Mine, Durham, 187 



The grit sill here made forty fathoms thick is usually di- 

 vided into two near the middle by a plate bed, and in that case 

 the separate parts are called the'High and Low Grit Sills ; but 

 in this situation, as far as I know, the only bed between them 

 is the thin stratum of carbonaceous shale mentioned above. 



The grit sill here is a soft sandstone not difficult to work, 

 and in point of situation among the strata of lead measures, 

 there seems to be some correspondence between it and the 

 firestone sill, No. 137 of Forster's Section. 



The drift alluded to, in which the trees were discovered, was 

 driven east from the engine-shaft about fifty fathoms, the whole 

 distance in the vein, having the north cheek or wall of the vein 

 on the left side, and the south or sun cheek (as it is called by 

 the miners) on the right side respectively. The vein stood 

 almost perpendicular, and was from three to four feet wide; 

 but instead of being filled between the cheeks with a matrix 

 of quartz and fluorspar, as in situations further west where it 

 had been productive of lead ore, it contained a compact stone 

 very much harder than the stratum of sandstone in which it 

 occurred. 



At the distance of fifty fathoms from the engine-shaft the 

 first tree was discovered, standing directly in the vein in close 

 contact with the north cheek, upon which an impression was 

 left corresponding to the indentations on the surface of the 

 tree. The diameter of the tree was twenty-two inches, and 

 the space between it and the sun cheek of the vein was filled up 

 with the hard veinstone mentioned above, by which it was 

 closely enveloped all around; but between the veinstone and the 

 tree was a thin black carbonaceous skin very smooth and 

 slippery to the touch. The substance of the fossil was a hard 

 stone ajiparently the same as the veinstone by which it was 

 surrounded. The workmen broke this tree to pieces, and found 

 it extend to and rest upon the thin stratum of carbonaceous 

 shale, below which it did not appear to penetrate, but it extended 

 upwards into the roof of the drift to an unknown distance: the 

 length taken down and broken to pieces was about four feet. 



The second tree, twenty inches in diameter, was met with at 

 the distance of five feet from the first, and, like it, was found 

 standing upriglit in close contact with the north check of the 

 vein ; the rest of the space between the cheeks being filled 

 up with veinstone as belbre. The same coaly matter occurred 

 between tlie substance of the fossil and its envelope, and in 

 this case the space contained also some ))articles of lead ore. 

 'I'his tree, like the first, rested ujjon the bed of carbonaceous 

 shale, and penetrated upwards into the roof to an unknown 

 distance. 



2 B 2 At 



