198 



ture, and many of the other known peculiarities in their consti- 

 tution. That some such agent must have operated appears to be 

 proved, (1.) By the formation of joints and fissures intersecting 

 the strata ; (2.) By the conformity of direction in these joints and 

 fissures ; (3.) By the internal movement of the particles or ingre- 

 dients of the vegetable mass among each other, whereby difi^erent 

 kinds of coal were formed in the same seam ; and (4.) By the fis- 

 sures and cavities in the coal being generally filled with pearl-spar, 

 which could only be derived from an aqueous medium impregnating 

 the vegetable mass, and holding carbonate of lime and magnesia in 

 solution. It was inferred from these and other circumstances, that 

 the agent which had operated on the strata after their deposition, 

 was subterranean heat. 



The rest of the paper was occupied with an explanation of the 

 convulsions which had occurred after the deposition of these strata, 

 and in consequence of which they had been thrown into the form 

 and position now presented by them. It was mentioned that the 

 very steep dip to the eastward, which the strata on the west side of 

 the Esk basin presented, was occasioned by the eruption of Arthur 

 Seat, Blackford Hills, and the other trap masses that occur along 

 almost the whole extent of the west side of that basin. 



It was next shewn, that bpfore the enormous quantity of vol- 

 canic matter which burst forth emerged from beneath the strata of 

 the district, these strata must have suflPered dislocations or cracks, 

 which would account for the slips and dykes that intersect the dis- 

 trict. It was also shewn, how these slips and dykes behoved to run 

 generally in a direction between N. and W., and cause the dislocated 

 strata to sink down on the north side of them, rather than on their 

 south sides. An explanation also was offered of the invariable rule 

 which had been found to prevail in this district as in others, that 

 if a slip haded or sloped from the vertical, the strata were always 

 lowest on the upper side of the slip. A reason was also assigned 

 for the fact, that in this district, the strata are not deranged (or in 

 other words, " thrown down" on either one side or other) by dykes, 

 but only by slips. 



