268 ^^ MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



The rough or cherry coal has the same three sets of fissures ; but the strength 

 and length of each set is in that kind of coal, not precisely the same as in the 

 splint coal. The set first mentioned, viz. those which are parallel to the surface 

 of the coal, are not so numerous or so wide or so extensive, as in the sphnt, so 

 that it has not the same tendency to a slaty shape ; moreover its cutters and its 

 slines are more nearly equal in these particulars ; and the consequence is, that the 

 rough or cherry coal when broken, assumes a shape or form more or less cubical. 

 Its vertical fissures intersect at an angle of about 85°. 



The same three sets of fissures are discoverable in the parrot-coal. But they 

 are greatly less numerous. The consequence is, that blocks free from cracks and 

 flaws, can be got of a much larger size in this kind of coal than in the other kinds. 

 These different fissures, in respect of continuity and width, are, in the parrot-coal, 

 very nearly equal ; — so that the blocks taken from it are, in shape, not very dif- 

 ferent from cubes. The acute angle formed by the sides is about 87°. 



These fissures have of course been produced at a period subsequent to that 

 of the formation, or at least the deposition of the beds they traverse. I have a 

 specimen of splint coal filled with the spines, teeth, and scales of fish. A fissure 

 intersects these organic remains, and has separated the relative parts by a very 

 visible interval. The fissure in the specimen alluded to, is about 1-1 0th of an 

 inch in width, and is fiUed with pearl spar. It is obvious, that not only the coal- 

 seam has been fissured, but that there has been a movement of the coal on one 

 side or both sides of the fissure. 



Before quitting the subject of slines and cutters, I may allude to a subject 

 which opens up a very interesting inquuy. I have said that these sUnes and 

 cutters intersect each other at a constant angle. I rather think also that they 

 lie invariably in a dh-ection, which is independent of the dip of the coal. I have 

 observed at a great number of places, the du-ections of the backs or lengthway 

 joints, and also of the cutters or end-joints. The former appear to me to run 

 every where in this district in a direction between N. and W. by compass. The 

 cutters, of coarse, therefore run between E. and N. I will afterwards revert to 

 this subject.* 



I have to add with regard to these fissures in coal, that many of them are 

 filled with thin films or veins of a white coloured spar. I gave to my friend Mr 

 A. CoNNELL a quantity of this substance to be analyzed, and he reports it to be 

 carbonate of lime, containing also some admixture of magnesia and iron. Some- 

 times this substance is found beautifully crystallized, coating di"usy cavities, in 

 the heart of the coal-seams. Sulphuret of iron, too, in a crystallized state, is 

 abundantly met with filling both cavities and fissures in the coal. 



* It is impossible to form any correct opinion on such a point as this, except upon a very exten- 

 sive range of facts. I have commenced a table shewing the direction of the backs and cutters in diffe- 

 rent parts of the district, which will be found in the Appendix B. 



