EFFECTS OF COAL ON HUMAN INDUSTRY. 5.31 
gion of this coal field are abundantly loaded with 
nodules of argillaceous iron ore, and below these 
is a bed of millstone grit capable of enduring the 
fire, and used in constructing the furnaces ; still 
lower is the limestone necessary to produce the 
fusion of the ore. PI. 65, Figs. 1, 2. 
The great kon foundries of Derbyshire, York- 
shire, and the South of Scotland, afford other ex- 
amples of the beneficial results of a similar juxta- 
position, of rich argillaceous iron ore and coal. 
“ The occurrence of this most useful of metals,” 
says Mr. Conybeare,* “ in immediate connexion 
■""ith the fuel requisite for its reduction, and the 
limestone which facilitates that reduction, is an 
instance of arrangement so happily suited to the 
purposes of human industry, that it can hardly 
fie considered as recurring unnecessarily to final 
causes, if we conceive that this distribution of 
the rude materials of the earth was determined 
i^ith a view to the convenience of its inhabi- 
tants.” 
Let us briefly consider what is the effect of 
mineral fuel, on the actual condition of mankind. 
The mechanical power of coals is illustrated in a 
striking manner, in the following statement in 
Sir J. F. W. Herschel’s admirable Discourse on 
Ifie study of Natural Philosophy, 1831, p. 59. 
“ It is well known to modern engineers that 
Geology of England and Wales, p. 333. 
