ii4 THE WORLD'S LUMBER ROOM. 



as we travel eastward, and approach the volcanic rocks of 

 the Ural Mountains, both are altered by the heat, and pass 

 into schists and quartzites. The muddy Russian plains are, 

 so geologists say, composed of some of the most ancient beds 

 of sediment in the world, and having been raised above the 

 waves ages ago, have never since been brought within their 

 reach or suffered much change of level. In age they corre- 

 spond with some of the Welsh rocks, but in Wales the mud 

 has been hardened and altered into slate, while in Russia it 

 remains pretty much in its pristine condition. 



One of the most ancient heaps of mud in England is now 

 dignified by the name of the Longmynd, or Long Mount, 

 which is ten miles long, and even now, though it has lost 

 much of its height, rises more than 1,000 feet above Church 

 Stretton, and is not less than 26,000 feet thick. Many of 

 the Longmynd rocks consist of innumerable thin layers, 

 some of them scarcely thicker than a sheet of paper, and 

 evidently once thin films of very fine mud and sand, though 

 now hardened into shales and slates of various tints, from 

 deep purple to grey and olive. 



A gigantic mud-heap this is, certainly, and more ancient 

 than we can easily realise, even though we know that the 

 whole of England to the east of it, with its thousands of feet 

 of sandstones, coal-beds, limestones, chalk downs, &c., has 

 been formed since it was deposited. 



The Longmynd rocks were originally deposited under 

 water in horizontal layers or films, such as those of the 

 Nova Scotia mud flats, the dark, gritty, coarse part of the 

 mud brought by each tide sinking first, and the finest 

 forming the top of each layer. But, whatever other changes 



