162 Mr. Williamson Peile's Description of a Group of Dylces. 



(No. 1.*), exceedingly hard and ponderous ; of which the main body of 

 the Dyke is composed. It is mixed, most strangely, with pieces of 

 Coal of all shapes and sizes, which have generally preserved their 

 quality and shining lustre, burn well, and seem in no way altered from 

 their original state, when clear of the Dyke. In some pieces, however, 

 that I have examined, I found the Coal altered. It had lost its texture, 

 M'as become soft, and greasy to the touch, and much resembled the out- 

 side coating of a piece of wood which had been charred, and buried in 

 a damp place. As this appearance frequently occurs when the Coal is 

 free from all Dykes, it cannot, however, be considered as characteristic 

 of the effect of the Rider. 



b. b. b. Black Metal Stone (specimen No, 2.), in small pieces, which 

 had protruded themselves from the roof into the Sandstone, for about 12 

 inches. They are not to be found in any other part of the section, and 

 belong to the stratum forming the roof of the seam. The colour is 

 somewhat altered. 



c. c. c. This singular substance is apparently aluminous, and both 

 its nature and situation in the section, are well shewn by the speci- 

 men No. 3. It will be seen to have forced itself into all the cleats, or 

 cleavages, of the Coal, and exhibits a shining polished face at its 

 contact with the Coal. In some cases Lime, and even Sandstone, 

 seem to have been substituted, and are also polished at their surfaces. 



Of the two sections before us. No. 1 is, in many respects, the most 

 singular, as being more varied, and the insulated situation of the pieces 

 of Coal more remarkable. The great body of Sandstone in the centre, 

 from which the branch, to the left hand, springs, was perfectly free 

 from any intermixture with pieces of Coal, but on the right hand, most 

 especially near the roof) the Coal and Sandstone were mixed up in the 

 greatest confusion. 



From the extreme point on the right hand, several very thin shoots 

 of the aluminous substance (c) were seen darting through the Coal, fol- 



* These numbers refer to specimens presented to illustrate this paper, and which may 

 be seen in the Society's collection. 



