Dr Thomson on a spcmtaneous emission of Gas. 69 



supposed change of dip) are undoubtedly under all the Glas- 

 gow coal beds. From the situation of the field where the evo- 

 lution of inflammable gas takes place and the dip of the 

 strata, I conceive that the rock or bed through which the 

 gas issues is the undermost bed of slate-clay in the preceding 

 sketch. 



When Mr Dickson began last year to work the lime-bed, 

 the workmen were so impeded by water that they could not 

 proceed in their operations. This induced him to set up a 

 small apparatus for draining the quarry. It was after this had 

 been acting for some time, that the issue of gas began to be 

 observed. Suspecting that the great quantity of water which 

 incommoded his quarry men proceeded from the rivulet, mak- 

 ing its way through the slate-clay bed, and rising to the lime- 

 stone, Mr Dickson employed persons to examine the course of 

 the rivulet, to endeavour to discover any indications of the sup- 

 posed sinking of the rivulet. The issue of gas through the 

 rivulet was observed and considered as favourable to this no- 

 tion, that the water in the quarry proceeded from the rivulet. 

 It was supposed to be common air issuing from the hollow 

 places under ground, as they became filled with water. But 

 some persons happening to apply a light to the gas, it took 

 fire, and showed that it was of an inflammable nature. 



Whether the gas had been issuing before Mr Dickson's at- 

 tempt to drain his quarry, or whether the issue was not the 

 consequence of this draining process, must be left to conjecture. 

 I am inclined to believe that the draining occasioned the ap- 

 pearance of the gas. Coal has never been wrought in the im- 

 mediate neighbourhood. The nearest workings are about three 

 miles to the south-west, and from the dip of the strata it is 

 impossible that the gas can proceed from them. The coal beds 

 in that place must be situated higher up than the stratum out 

 of which the gas comes. I am not aware of any coal mines to 

 the north-east nearer than eight or ten miles. I think it pro- 

 bable from this, that some cavity exists in the earth situated 

 below the slate-clay, through which the inflammable gas issues, 

 and situated to the north-east of it — that a bed of coal forms 

 the floor of this cavity — that water had got access to this ca- 

 vity, and, acting on the coal, had occasioned the evolution of 



