148 
froth 
such, or tinder a superior degree of expansive force, the 
following important truths may be learned : That the 
quantity of oxygen which enters into our atmospheric 
compound is generally more fit for the manufacture of the 
superior qualities of crude iron than any mixture which 
may be furnished by the addition of water : that, although 
the decomposition of water, by furnishing a superior quan- 
tity of oxygen, and by throwing off a relative proportion 
of caloric, increases the effects of combustion immediately 
in the vicinity of this chemical analysis ; yet, as the wa- 
ter had previously abstracted the heat necessary to its de- 
composition from the inferior strata, a greater quantity 
by no means exists in the furnace. The water, in fact, 
only serves as a medium to convey the heat from one par- 
ticular spot, but, by attempting to fly off with it, meets 
decomposition, and renders up not only the abstracted 
heat, but that which was contained in the oxygen of its 
decomposition* . 
4th, The compression and velocity of the air discharg- 
ed into the furnace, considerably affect the results of the 
smelting operations. In the consideration of this subject 
the various qualities of coals will be found to have an in- 
timate connection with the area of the discharging-pipe 
and the compression of the blast* It lias already been 
more than once observed, that a soft or mixed quality of 
coal is more susceptible of combustion than either the 
splint or clod- coal : the consequence of this is, that, un- 
less the necessary compression of air is used, decompo- 
sition is too early accomplished, and the coaks become 
oxygenated by combustion in a greater ratio than is pro- 
per for the carbonatloii of the metal. To avoid this the 
•column of air ought to be discharged, in the case of soft 
* The introduction of vapour or steam is not well understood., 
I have seen steel made by introducing steam to melted iron $ but 
I do not understand the way in which it operates.. 1\ C. 
