Mr. Forster's Notice of a Basaltic Dyke. 4>5 



doubtless, from the surrounding strata preventing the expansion which 

 takes place in the artificial coking of Coal,) that it would have been 

 nearly impracticable to have continued the drift through it ; it was, 

 therefore, found preferable to raise the drift into the superincumbent 

 stratum of hard Metal Stone, intermixed with Sandstone, and in this 

 stratum it was continued (having for its floor the mixed bed of Basalt 

 and charred Coal), until it intersected the Basaltic Dyke (coloured red) 

 at D. 



Precisely at the point of contact between the stratum of hard grey 

 Metal Stone and the Dyke, a leader of charred Coal was found, ex- 

 tending upwards from the mixture below, and penetrating the exterior 

 crust of the Dyke, as represented by the specimen, No. 1. It is worthy 

 of remark that, with regard to its position, this leader was precisely simi- 

 lar to those generally met with in common Dykes. The Dyke was 

 found to be 2^ yards in thickness, underlying to the north about 15 

 inches per fathom, and composed of compact Basaltic matter. The 

 strata were thrown upwards 2 fathoms on its south side, as represented 

 in the section. No opportunity occurred of observing the effects of the 

 Dyke on the Main Coal Seam, adjoining its south, or rise side, but the 

 floor, or " ikill," of the seam, through which the drift passed, did not 

 appear to have been in any way affected by it. 



At the distance of 10 feet from the Basaltic Dyke, a common Dyke 

 (coloured brown in the section) was intersected by the drift, and found 

 to be an upcast to the south, of 6 fathoms. This Dyke in every respect 

 resembled those commonly met with in the Coal measures, nor did any 

 thing in its appearance, indicate its proximity to the Basaltic Dyke. 

 The drift was continued forward for about 40 yards beyond this 6-fa- 

 thom Dyke, and the strata were found to follow their regular course 

 without further interruption. 



Subsequently to the driving of the drift, the sinking of the WiUiam pit 

 was commenced on the south, or rise side, of these Dykes, and about 19 

 yards to the south of the point where the Basaltic Dyke reaches the 

 surface. In the progress of sinking this pit, the beds of Sandstone, or 

 Post, were found to have increased very much in thickness, as compared 



