10 April, 1841.] 



startling ; especially since the terms heavy, hard and tough, are 

 generally applied to the one, and light, soft and friable or tender, to 

 the other. It is nevertheless true, that strong mechanical resem- 

 blances exist ; and the more minutely we examine the two varieties, 

 the more shall we be impressed with the conviction of the import- 

 ance of the resemblance. 



In the first place, the coal of all coal measures has a series of 

 partings parallel to the floor or bottom of the bed on which it rests, 

 and to the cover or roofing under which it lies. These are as dis- 

 tinct in inclined and vertical beds as in those which still remain 

 horizontal. 



In the second place, the connection between the coal and its under- 

 lying slate, as well as with its top slate, is so definite and well under- 

 stood, that it serves to determine the true original position of coal 

 beds, which have been so far disturbed as to be turned nearly up- 

 side down ; of which examples are not wanting. These character- 

 istics are found in beds of both kinds of coal. 



In the third place, there is most commonly a fracture or division 

 of the coal in some direction (which, for the same bed, is gene- 

 rally continuous,) and nearly at right angles to the planes of de- 

 position. 



Fourth, a third series of divisions by vertical planes, called cross 

 partings, inclined to the last mentioned. This system of planes is 

 not always continuous throughout the bed, but varies in the differ- 

 ent plies. 



The principal vertical divisions are known to miners by the 

 names of "cleats" or " slines," and sometimes by that of "grains." 

 The direction in which these run, seems to determine the manner 

 of working out the coal ; for in attempting to separate large masses 

 from their natural position by means of wedges, it is only in the 

 direction of the cleats that the separation can take place. In in- 

 clined beds, from which the coal is to be extracted by a slope or 

 rail-road laid down on the floor of the bed, it is a great convenience 

 to have the cleat lie in a direction diametrically across that of the 

 slope, or in conformity with the strike of the bed ; for then in run- 

 ning a drift from the bottom of the slope horizontally along the bed, 

 and afterwards carrying the workings upward, the cleat will always 

 face the miner, and he will be enabled to obtain heavy falls of coal 

 by undermining and wedging down. 



