MR MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 267 



parts of the deposit now referred to, present a complete contrast to the other 

 parts. 



VI. Having descrihed the general arrangement and position of the strata, 

 and said something of the varying character of particular strata, I should wish 

 next to offer some general remarks on the internal structure of the strata. On 

 this subject, however, I regret to say, that my information is exceedingly scanty. 

 But if for no other pm-pose, than to shew how much remains to practical men on 

 this branch, I will state the little that I have gathered in my rambles. 



(1.) I begin with coal, because the qualities of that mineral have naturally 

 been more closely and accurately examined than those of any other. 



There are three or foiu* different kinds of coal in the district. The most 

 easily distinguishable are the splint, the cubical or cherry or cheery* coal, and 

 the parrot. Each of these can be pointed out at once by coUiers, as each of them 

 possesses characters, which to their eyes are obvious and decisive. Each kind of 

 coal has a different internal organization. That difference is shewn in various 

 ways. I may mention one way in which it is very easily and very decisively 

 shewn. If a large fragment is smashed with the hammer, or dashed violently to 

 the ground, it will be foimd to have been intersected by a number of fissures, 

 which give a peculiar shape and form to the morsels broken off. These fissures 

 ^ cause each kind of coal to break up in one way, rather than in another. 



In the Splint-cosl there are three sets of fissures, (1.) one set parallel with 



f the surface of the coal-seam ; (2.) another set perpendicular to the surface ; and 



(3.) a third set, also perpendicular to the surface, and intersecting the second set 



[ at a constant angle. The blocks are not in the splint coal exactly cubical, — they 



form thin tabular masses, owing to the predominance in them of the longitudinal 



fissures. These thin tabular masses are not rectangular in shape. The vertical 



fissures intersect each other at an angle, which is between 80° and 83°. Farther. 



[the figure of the fragment, on its surface, is rhomboidal, — that is to say, one side 



I is always longer than the side intersecting it. The reason appears to be, that the 



I two sets of vertical fissures which form these sides, are not equally continuous or 



open. So that there is always a tendency in the coal to spMt in one way more 



[than another. Those fissures which mn farthest and are the widest, of course 



form the longest side of the rhomboid. These are called sUnes, backs, or length- 



f way joints, in the language of the colliers. The other set are called cutters or 



: end-joints ; and both sets are made good use of, in working the coal, as they 



I allow the wedges to be inserted, and enable the collier to bring down masses of 



coal of any size he pleases. It is in consequence of these three different sets of 



fissures, that the sphnt coal breaks so readily into oblong tabular masses. 



* So called, probably, from its blazing better than the other kinds of coal. 



