172 Scientific Intelligence — Geology, 



shaft was in fact opened upon the most elevated portion of the 

 workings, and all the galleries communicating with it had a ra- 

 pid descent, following the inclination of the bed, which was at 

 an angle of 18° or 20°. The escape of the gas through this 

 depth of water continued without interruption, with the same 

 intensity, during several months. I may add, that, after I 

 had caused a horizontal floor of planks of fir to be constructed, 

 and covered over with ^about six feet of stiff clay, well pressed 

 down, and sunk to the bottom of the shaft, the gas escaped much 

 more sparingly across the fissures of schistous rock, but still in 

 very considerable quantities. In those beds which retain the 

 hydrogen only under such great pressure, it is manifest that the 

 quantity will vary to a very trifling extent, with the variations 

 of the barometer. Nevertheless, in certain circumstances, the 

 air in the mine is more charged with gas, as during the time of 

 a storm, when the barometer is low, than in calm and fine wea- 

 ther, with a dense atmosphere." In the work to which this no- 

 tice is, as we have said, a kind of supplement, Mr Buddie, when 

 treating of the explosion which took place on the 3d of August 

 1830, in the coal-mine of Jarrow, points out two causes which 

 are the cause of explosions in the coal-mines in the north of 

 England ; 1^^, The numerous fissures and rents in the encasing 

 rock, which thus form cavities filled with gas, whence it issues 

 in greater or less quantities, according as the pressure of the 

 atmosphere is more or less; 2cZ/z/, Blind cavities in the coal- 

 seam itself, or in the surrounding rock, whence the gas suddenly 

 escapes, when the galleries reach and open them up. M. Combes 

 confirms the existence of this second cause of disengagement, 

 from the occurrence of accidents which have happened in French 

 mines; and, among others, by an explosion which happened on 

 the 10th of April 1824, in the coal-mine of Ronchamp, in 

 Haute-Saone, when twenty miners were killed, and sixteen most 

 severely injured. According to the reports of the engineers^of 

 the mine, inflammable gas had previously very rarely, and in 

 very small quantities, manifested itself in this mine. A trifling 

 disengagement had taken place in a try-work which was begun 

 at the bottom of the pit of St Louis, close to a fault. In a re- 

 port which M. Thirria gave in to the Director-General of 

 bridges, roads, and mines, he remarks, " It was imagined that 



