lOG 



shaft of basalt pierces the underlj-ing strata. This is detailed fixlly in Sir K. 

 Mvirchison's larger work. He there describes how the coal seams were found 

 to assume a sooty appearance as they approached the wall of Dhu-stone, and 

 that they were at last all cut off by it, and yet that the contents of these 

 measures gave, under the blow-pipe, bituminous products, thais in every way 

 proving that the core of basalt had been intruded after the formation of the 

 coal strata, and not only so, but had by its great heat changed the form — burnt 

 into cinders and soot — of their contents. 



In this very hard and pennancnt rock may be seen the cause to which 

 we chiefly owe the existence of this and the neighboiu-ing Clee Hill, of the 

 "Wrekin, and a few other hills within this horizon. These hard rocks have 

 been a standing barrier to the ceaseless forces which have worn away and 

 carried down to the sea the enormous masses of strata through which they 

 were protruded. "When you look to the Brown Clee HiU, about four miles to 

 the north of this, and see that the coal strata on the summit of it, like the 

 coal strata on the summit of this, are nearly horizontal — if you travel 

 northwards to Coalbrookdale and the black country, as it is called, and observe a 

 similar fact, and that under these lie in regular succession the strata of the 

 Millstone Grit, and under that, the Mountain Limestone, and under that, the 

 Old Eed Sandstone — when you see that these strata have been cut off abruptly, 

 and that if they were continued from one chain of hills to the other they 

 would just coincide — (indeed in the minor divisions of the coal seams, 

 these successive layers are said to be traceable over very great areas). 

 When you consider these facts, it is impossible to resist the inference that these 

 Coal deposits were at one time all connected, and formed one great plain, one 

 flat swamp. It has usually been sujiposed that these gi-eat swamps were the 

 estuaries of vast rivers, and as vast rivers imply still vaster continents upon 

 which the rain would be precipitated, imagination might construct, ad libitum, 

 pile on pile of upland and mountain somewhere. But where ? That 

 question is not easily answered. Iily friend Mr. Salter, however, has 

 shown that not only a much simpler mode of formation of these coal 

 fields is possible, but that there are positive evidences that it was the true 

 one, and that is, that these tracts of forest were marine marshes. Such are 

 occasionally found in the tropics in the present day, and not only the flora 

 themselves, but the existence on them of fossil sea worms, proves their marine 

 origin. 



I have next to call your attention to a period in the history of our 

 globe when all these rocks had long been formed at the bottom of the sea, 

 hardened into rock, upheaved, sculptured out into hills and valleys, other 

 rocks formed on their edges, and then in tui-n denuded, each one of these 

 oi>i rations involving countless time. We at last amve at a period when the 

 land was gradually assuming the shape we now behold it, and in that distant, 

 low lying country to the west wo behold the clearest traces of this last process. 



