UNCLE IN ENGLAND. 117 



beds of peat alternate with beds of mud or sand, 

 which must have been deposited in the bottom of 

 lakes, and in these cases they appear something 

 like an incomplete coal formation. 



" In a short time," continued my uncle, " we 

 shall have a better opportunity of studying this 

 curious substance, if your interest in it continues, 

 when we are in Ireland, as that island contains 

 a greater proportion of bog than any country 

 with which we are acquainted." 



" My interest in it, my dear uncle, I replied, 

 is not very likely to fail while I have your kind 

 assistance ; but as we are as yet in a coal country, 

 perhaps you will tell us something of the forma- 

 tion or origin of that mineral." 



" There is no possible doubt," he said, " that 

 the general origin of coal must be referred to the 

 vegetable kingdom; and I began with peat, to 

 show you how masses of vegetable matter may 

 be collected in thick and very extensive beds, 

 ready for whatever process nature may after- 

 wards employ in converting them into coal. 

 Some species of coal are merely fossil wood (or 

 lignite} impregnated with bitumen : the branches, 

 trunks, and roots, though closely pressed together, 

 are scarcely altered in texture, in some places ; 

 while in others they gradually lose every vege- 

 table feature, and the substance in colour, lustre, 

 and fracture, resembles pitch. Of this nature is 

 the Bovey coal of Devonshire, and the Surtur- 



