178 WHAT WE OWE TO OUE COAL-FIELDS. 



lectually as well as materially, is a thing dependent alone 

 upon the existence of a Coal-formation. There is no arti- 

 ficial source of heat (and heat is the spirit of all force) so 

 compact, so portable, so safe, and so readily available as 

 coal ; no substance so adaptive, so strong, and so enduring 

 as iron. There is no artificial power so titanic, and withal 

 so submissive and tractable, as a few pounds of ignited 

 coal acting through the medium of water; no harness 

 save one of iron sufficiently strong to yoke that giant power 

 in the services of human industry. These two substances, 

 coal and iron, have been the main factors in all recent pro- 

 gress ; and that which most broadly distinguishes the 

 Britain of the present from the Britain of the preceding 

 centuries is the extended and extending use of these sub- 

 stances through the instrumentality of the steam-engine. 

 -NTor is it for these two minerals alone that we are indebted 

 to the Carboniferous system ; for from the same formation 

 we obtain numerous other products, all useful in the arts, 

 and some of them indispensable auxiliaries to the employ- 

 ment of coal and iron. These are the sandstones, lime- 

 stones, marbles, fire-clays, oil-shales, alum-shales, and cop- 

 peras-shales, and not unfrequently in some localities the 

 ores of lead, zinc, and silver. 



Taking COAL as the chief product, we find it in many 

 varieties and in all degrees of purity: Caking coal, like 

 that of Newcastle, which is tender and bituminous, and 

 cakes together in burning ; cubic or rough coal, which is 

 harder, burns open, and leaves much ashy residue \ splint 

 or slate coal, like that of Fife, which is hard and laminated, 

 and burns open, with the emission of great heat ; and 

 cannel or parrot coal, compact and jet-like in texture, rich 

 in bitumen, and now chiefly used in our gas-works. One 

 or other of these varieties is found in every coal-field, and 

 according to its quality (for, like all mixed rocks, coal is 



