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 described 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 purpose, 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 four 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 colliers, 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 found 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-coal there are three sets of fissures, (1.) one set parallel with 

 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 

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

 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 split in one way more 

 than another. Those fissures which i-un farthest and are the widest, of course 

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

 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 

 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 splint coal breaks so readily into oblong tabular masses. 



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



