166 THE OLD COAL-MEASURES. 



the appearance presented by the "upthrows and down- 

 throws," the " faults and dykes " of many coal-fields, and 

 especially of those of the Scottish Lowlands. 



Composed, like other systems, partly of stratified sedi- 

 ments, and partly of unstratified masses which were the 

 volcanic products of the period, the Coal-measures present 

 no great difficulty as a Bock- Formation, and few of its 

 strata have undergone much metamorphism or internal 

 change, unless where in contact with igneous eruptions. In 

 its stratified rocks we perceive the obvious sediments of 

 seas, lagoons, and estuaries, the relics of shell-beds and coral- 

 reefs, the vegetable growths that accumulated for centuries 

 in swampy morasses,* flourished in the virgin forests, or 

 tangled rankly in the river-jungle ; and in its unstratified, 

 the eruptive mass, the molten overflow, and the frequent 

 shower of dust and ashes. Interrogated as mere rock- 

 masses, they expand overflow after overflow, and stratum 

 upon stratum, like the leaves of a mighty volume, and tell 

 of gigantic rivers and estuaries, of shallow seas, tides, and 

 ocean-currents, of low-lying continents and volcanic archi- 

 pelagoes, of shell-beds and coral-reefs, of vegetable growth 

 and vegetable drift, of rains that fell, winds that blew, and 

 suns that shone and gladdened the face of nature even as 

 they do now. Of all this, and much more, these coals and 

 sediments bear abundant testimony; and interesting as it 

 must ever be to the educated mind to trace back the unity 



* A curious proof of the morass or swamp-growth of many of our 

 coal-seams, is to be found in the narrow winding " wash-outs " by which 

 they are frequently intersected. These " wash-outs" of the miner are 

 stream -like courses from which the coaly matter has disappeared, its 

 place being taken by stony substances. They have been clearly runnels 

 or water-courses that threaded their way through the swamps, and 

 thereby prevented the accumulation of the vegetable matter, just as at 

 the present day our peat-mosses are cut into channels by the streams 

 that may drain their surfaces. 



