258 Mr. AiKiN on a Bed of Trap ^ &c. 



the engine and bye pits, which are the nearest to the fault, the 

 same bed is 27 feet thick. The actual junction of the greenstone 

 of the bed with that of the fault has not indeed been proved, but 

 from the very little unexplored space^ at present between them, 

 there can exist but little doubt I imagine as to the fact. Now, 

 though it is possible that the outburst of the greenstone (supposing 

 it to be really a bed) may so coincide with the elevation and cur- 

 vature of the ridge as, with a thickness of no more than about 30 

 feet, to give the appearance of a rock 60 or 100 yards across, yet 

 this hypothesis is scarcely consistent with the rapid increase of the 

 angle at which the strata above the greenstone bed are elevated in 

 the vicinity of the green rock fault, advancing in a few yards from 

 6° to 25°. The absence of the greenstone bed in the pit D. 

 though it is full as near the line of bearing of the fault as the 

 engine and bye pits are, is a further support of the opinion that I 

 have hazarded. . Upon the whole, then, I am inclined to consider 

 the green rock fault as a fissure in the coal field, filled up by green- 

 stone, and the supposed greenstone bed as a wedge-shaped pro* 

 longation of the same. 



With regard to the mode In which thi« and similar fissures have been 

 filled, whether by deposition of the constituents of greenstone from 

 solution or suspension in a superincumbent aqueous fluid, or by the 

 bursting from below upwards of earthy matter, either melted or in 

 the state of boiling hot mud, like the mud-volcanoes of Mexico 

 and of the island of Taman in the sea of Asof, I shall not pretend 

 to decide. 



