46 Mr. Forster's Notice of a Basaltic Dyke. 



with the same strata in the dip, or north side, of the Dykes, as will be 

 seen by referring to the section. As similar changes of thickness take 

 place, however, in many cases where the strata are broken or interrupted, 

 it does not follow that the change here is at all connected with the Ba- 

 saltic Dvke. 



The Yard Coal Seam, which was cut at the depth of 1^ fathoms, did 

 not appear at all affected by the Basaltic Dyke, yet on coming to the 

 Five Quarter, or Crow Coal Seam, at the depth of 26|^ fathoms, and at 

 a horizontal distance of 32 yards from the Basaltic Dyke, a very re- 

 markable appearance was presented ; a bed of Coal, about 8 inches in 

 thickness, extending over the whole of the bottom of the shaft, was im- 

 mediately underlaid by a bed of compact charred, or carbonized. Coal 

 and a bed of Basalt, abutting against each other, each of them being 

 10 feet thick, or about twice the thickness of the Five Quarter Seam. 

 The relative position of these two beds will be better understood on re- 

 ferring to the section, where, it will be observed, that, at about one-third 

 the distance from the dip, or north side of the shaft, the bed of carbonized 

 Coal (dotted black), which doubtless represents the Five Quarter, or 

 Crow Coal Seam, is entirely cut off, and its place occupied by a stratum 

 of Basaltic matter (coloured red) of corresponding thickness and incli- 

 nation, extending towards the rise. Between these two beds a perpen- 

 dicular fissure, of about 3 inches in width, was found ; its sides lined 

 with crystals of Carbonate of Lime and Iron Pyrites. It is by no means 

 the least remarkable feature in this stratified mass of Basaltic matter, 

 that it occurs on the opposite side of the shaft, as contrasted with the 

 Dyke ; and it is also worthy of remark, that the 8-inch layer of Coal 

 extends equally across both the Basalt and Coke, and appears to be very 

 slightly, if at all, carbonized by its proximity to the Basaltic matter. 

 There has been no opportunity of tracing the stratum of charred Coal 

 towards the Dyke ; hence the changes it may very probably undergo 

 before it reaches that point, are unknown. With regard to its stratifi- 

 cation, however, it may be fairly inferred that it will, like the Main Coal 

 Seam and accompanying beds, be depressed by the 6-fathom Dyke, and 

 it has been drawn on the section accordingly. How far the 10-feet 



