166 ON THE ORIGIN OF COAL. 



that the vegetable matter now forming Coal was 

 drifted into the places where it is found ; else we 

 should expect fully as great, if not a greater, 

 amount of vegetable matter, where we find 

 evidence of a strong current. 



As before stated, rough gritstones, containing 

 rounded pebbles of quartz, abound in the lower 

 Coal-field ; whilst the middle and upper measures, 

 reaching to a thickness of four thousand four 

 hundred and seventy feet, as far as 1 know, have 

 never yet afforded a piece of mineral matter in 

 their sedimentary deposits, of the size of a small 

 pea. In two seams of Coal, namely, the four 

 feet mine at Patricroft, and a small seam under 

 it, the same mine at Pendleton, I have obtained 

 rounded stones of several pounds in weight, but 

 as both these specimens came from the neigh- 

 bourhood of great faults, probably they may have 

 been brought to the places where they were 

 found, by other causes than currents of running 

 water. They, however, are interesting, and 

 very difficult to account for, being well rounded. 

 Their composition is the same, though found in 

 different seams and distant places, being of hard 

 crystalline quartz, more resembling Gannister 

 than any other stone in the carboniferous series. 



