Correspondence. 



in 



faglc>m m 



The dyke represented by fig. 1 was met with in the mine of Sallun- 



chee, at a distance of about 70 yards from 



the entrance; No. 1, in an Easterly direction. 



It runs SE., and NW. and dips about 84° to 



the NE, while the coal dips about 10° to 



the SSE. 



The diagram No. 2 represents a dyke which I discovered in the bed 



of a torrent which runs close by the same mine of Sallunchee, a few 



yards above the new bridge. This one, I think the most interesting 



of the three, on account of its 

 peculiarities. It is divided into 

 several branches, and some of 

 these are again united by cross 

 veins, as in the diagram. Ano- 

 ther of its interesting points is its containing small pieces of coal, 

 entirely enveloped in its mass, and converted into a substance in every 

 respect the same as anthracite, and columnar. 



Fig. 3 represents the cropping out of the third dyke. It is at 



Ranigunge mine, and lies between the Shaft No. 21 



S6af£<M>2i and the new Engme shaft. It has not been reach- 



■f~\ ed by the underground workings, but can be traced 



• on the surface in an ESE. direction. It most 



i 



* likely dips to the SSW. for a contrary dip would 

 throw it so far from the foot of the Shaft No. 21, 

 that it would be too far off to affect the coal there 

 in the manner it has. 



d- d- d/cl/ <H/ 



fy3 



The rock of which they are composed is, I think, the same in all, but 

 its characters are too confused for me to give it a specific name, so that 

 I have contented myself with ,the generic name Trap. — It partakes of 

 the nature of porphyry in some parts, in others it has more resem- 

 blance to greenstone, while specimens from No. 1 appear to be amyg- 

 daloid. However these rocks are so nearly allied that it is of little 

 importance to separate them. 



The Dyke No. 3, I suppose to be of the same rock as the other two, 

 because that part of it which is near the surface, and partially decom- 

 posed, bears a sufficient resemblance to the others in the same position 

 to warrant the inference. 



It has however its peculiarities. It contains in some parts a great 

 number of small nodules of crystalline carbonate of lime, some of which 

 are covered on their surface with very small crystals of iron pyrites. 



