168 Mr. BuDDLE on Subsidences in Coal Pits. 



to ascertain the fact, I preferred taking the line of the railway, which gives the 

 true result in that part. 



The metal-stone strata also considerably exceed in thickness the beds of sand- 

 stone, and operate to make the depression less than that noticed in the former 

 instance. 



In the present working of No. 2. (the five-quarter seam) the effects of the frac- 

 tures occasioned by the former excavating of the lower seams are clearly discern- 

 ible. Innumerable cracks pass through the coal and pavement, as well as through 

 the roof-stone, in a vertical direction, but they are perfectly close, except round 

 the margin of the settlement. Here a breaking and bending of the seam, pave- 

 ment and roof-stone have taken place. The cracks in the pavement are fre- 

 quently open, forming considerable fissures ; the coal is splintered and the roof- 

 stone is shattered. This is not, however, the case in the interior of the settle- 

 ment ; on the contrary, the cracks are quite close, and the pavement is as level 

 and smooth as if it had never been disturbed. The cracks in the coal pass through 

 the seam without having injured, splintered, or triturated it on the sides of the 

 cracks, as is generally the case with the natural hacks. The only alteration pro- 

 duced has been to render the coal more tough and woody, as the colliers call it, 

 in working than it was before these fractures took place. This effect may be attri- 

 buted to the escape of the gas by the cracks ; and it sometimes takes place from 

 other causes, when the coal is said to be winded by the colliers. 



The smoothness of the pavement in the interior of the subsided tract is due, 

 probably, to the pressure of the superincumbent mass, which is partially, if not 

 completely, detached from the surrounding strata, and its line of pressure is di- 

 rectly downwards. 



I would here observe, that I never noticed any tendency to a sliding or sideway 

 movement in any subsidence of strata occasioned by the working of coal, except 

 the slight obliquity occasioned by the off"-break at the sides of the settlement, as 

 already described. 



The facts here stated fully confirm, in my humble opinion, the hypothesis 

 adduced in your ' Elements,' (p. 122) ; and when our pigmy operations can produce 

 such palpable and analogous phsenomena — what stupendous effects upon the sur- 

 face of the globe may we not imagine the grand excavator of nature — the volcano 

 — capable of producing ! 



Second creeps, or subsidences of the surface, sometimes occur from water being 

 suddenly let off" from old colliery-workings, after having been a long time pent up 

 in them. 



JOHN BUDDLE. 



Walls End, Newcastle-upon-Tyne, 

 August 22nd, 18^9. 



