264 COAL FIELDS. 



in all their productions and phenomena, but it 

 explains many things which otherwise are puzzles 

 in geology; and it enables even those whose means 

 and opportunities are the most limited, to turn 

 even the progress of the most common labour into 

 a means of instruction and pleasure. The digging 

 of a quarry, or even the cutting of a drain, may be 

 made a study of nature, and the hand that works 

 may work with more ardour and success in conse- 

 quence of there being instruction, and consequently 

 pleasure in the working. 



The coal mines, from the e'xtent and depth to 

 which they have been worked, are perhaps the 

 best places for observing the traces of that work- 

 ing. The coal itself has been vegetable matter, 

 for there are vegetable impressions in it. It lies 

 generally in basins, and there are in most cases 

 many seams, and some of them deep below others, 

 so that the " coal measures," or strata in which 

 the coal is found, have been formed gradually. 

 They consist chiefly of limestone clay, iron stone, 

 and sand stone ; the accumulation of which must 

 have required a long period of years. But they 

 also show traces of volcanic action, in the " dykes 

 and cutters," by which they are intersected, and 

 which often throw the strata out of the plane, so 

 that the coal is higher on one side of the dyke 

 than on the other. Those dykes are frequently 

 " whinstone," or allied to basalt ; and there are 

 cases in which the basalt has issued in quantity 

 and formed " caps " on the top of the other strata. 

 The coal-field in the south of Fifeshire is remark- 

 able for those caps, which there form very beau- 

 tiful conical hills, locally termed "laws." The 

 top of one of these, " Kellie law," is, under the 



