T2 Mr Bald on the spontaneous emissions of Gas. 



operation in the lime-quarry took place, as particularly no- 

 ticed by Dr Thomson ; but that inflammable gas issued from the 

 cutters of this lime rock in great abundance has been known 

 to me for at least twenty -five years; and it was a common prac- 

 tice of the workmen to keep the gas burning as a matter of curi- 

 osity. It was then concluded that the gas was generated in the 

 coal which hes immediately under the limestone, and if the slate- 

 clay under the coal is full of cutters or fissures, an additional 

 supply of gas may proceed from an under-coal ; or, if the slate- 

 clay is of a close and impervious nature, and the coal full of fis- 

 sures, a slip of the strata, so common in coal-fields, may connect 

 the whole of the coals of this place together, and produce an 

 uncommon issue of inflammable gas. 



This is a circumstance well known in the colheries situated 

 on the rivers Tyne and Wear in the north of England ; and it 

 is in this instance of slips or dislocations of the strata having 

 an open vize or fissure, that those terrible and most dangerous 

 issues of inflammable gas, known there by the name of blowers, 

 are found. These, when first struck, issue with the force of 

 steam from an engine boiler, and with uncommon noise ; and 

 this issue continues sometimes for many years. 



It is, I think, probable, that the gas has issued from the bed 

 of the brook, as noticed by Dr Thomson, for many years past ; 

 and the circumstance of the workmen looking carefully for the 

 ingress of water into the quarry from the bed of the river, 

 may have led to the discovery of the issuing of the gas ; and I 

 think it very likely with Dr Thomson, that the water filling 

 the excavated part of the lime rock may have greatly contri- 

 buted to the more violent issue of the gas at the time when Dr 

 Thomson made his observations; besides, if the slate-clay is 

 of the bituminous kind, it may be another source from which 

 the gas comes. Some of this kind of slate-clay burns with a 

 strong and lively flame, but the bulk of the slate-clay is very 

 little altered by the burning 



Dr Thomson notices, that at the excavation made in the sur- 

 face soil, where the gas had continued burning for several 

 weeks, the clay had the appearance of pounded bricks. I have 

 observed that when miners kept the gas which issued from the 

 coal burning constantly, and which had a flickering flame, for 



