president's address. 179 



subjected to the action wLiich rounded and smoothed the adja- 

 cent rocks. The main dyke, which here runs nearly E. and W., 

 is well seen, being quarried for road material. Where it is thus 

 laid bare it is seen to be crossed nearly at right angles by ano- 

 ther and lesser dyke, locally known as the Doghole Dyke. The 

 effect of this is to break the line of the main dyke at the inter- 

 section by exactly its own width (twenty-two yards), but with- 

 out changing its direction. The effect of the dyke on the coal 

 was of course not visible at the surface, but specimens were pro- 

 duced, and Mr. Dixon, of Cockfield Colliery, was present, and 

 supplied ample and trustworthy information. Dr. Philipson read 

 an interesting paper descriptive of the dyke by the late Mr. 

 Witham, of Lartington. The members verified for themselves, 

 as far as possible, the accuracy of Mr. Witham's description as 

 to the effects upon the coal and sandstone in contact with the 

 dyke ; the amount and direction of dislocation caused by each ; 

 and the extent of shrinkage in cooling, &c. The effects on the 

 coal appear to be very remarkable. In contact with the dyke 

 it is converted into a sort of indurated soot (dawk or swad), the 

 five-quarter seam being reduced to nine inches in thickness; and 

 it is more or less changed to the distance of forty-five yards on 

 either side. 



The party visited the outcrop of the coal seam in a neighbour- 

 ing gill ; and, having spent a couple of hours very instructively 

 at Cockfield, proceeded to Eaby, which, by the kindness of the 

 Duke of Cleveland, was thrown open to them. After a pleasant 

 walk the grand old castle was seen, standing stately and grey in 

 its noble park, with little in its aspect to disturb the visions of 

 the past with which fancy loves to surround such a place. I will 

 not detain you with what occupied the party at Raby for a couple 

 of delightful hours. Afterwards they proceeded to Staindrop, 

 where the church and its monuments were duly visited. After 

 dinner Mr, T. Thompson exhibited a fine specimen of Acherontia 

 atropos taken at Ravensworth shortly before. 



The Fourth Meeting was at Dunstanbro' on the 16th of 

 August. Again the weather proving propitious, between forty 



