General Refleciions on Heat. 31 
sent is a bright reality. But whence does steam derive this 
power? What renders its force so omnipotent, that, asin Per- 
kins’s engine, a bubble can lifta ship over the waves? I an- 
sWer, itis HEAT. 
IV. Over the laws of cHEMICAL aPFiniITy, the same agent 
exerts a powerful contro]. If we attentively consider the state 
in which all bodies are found, whether solid, liquid, or eri- 
form, whichever of these forms the body is in at any given 
moment, depends on the quantity of heat that happens to be 
combined with it. Were it not for this agent, all bodies, if 
we could suppose them to exist without it, would be in the 
state of solids. Water and all liquids, air and all gases, are 
maintained in their respective states by its influence alone. 
In the production of all chemical phenomena, indeed, no 
agent is of so frequent recurrence as this. Some elements 
We unite into a compound by heat; some compounds we 
resolve, by the same means, into their elements. It is owing 
to this dominion which heat exerts over chemical affinity, that 
it becomes the chief resort and dependence in so many of the 
rocesses of the arts, both the useful and the ornamental. 
he greater number of the arts, indeed, are so entirely de~ 
pendent on this power, that they can advance hardly a step 
without it. Iron, from its intimate relation, and indispensa- 
Ble utility in all the mechanical operations, has been properly 
denominated ‘the soul of the arts;’ but if we go one step 
further, we shall find that iron itself is not, and could not be, 
either reduced from its ores, or wrought into the forms of 
utility and ornament, without the aid of heat. To pass over 
its agency in communicating to steam that elastic force, by 
which, in the most improved operations, it is made to lift the 
ore from its subterranean bed, let us suppose it raised to the 
surface, and thence letus trace it through the transmutations 
to which it is afterwards subjected. What fires are kindled 
over it to bring it to the metallic state! These are renewed | 
to convert it into steel. By heat itis manufactured into those 
numberless forms that every where meet our eyes. Fourcroy 
sums up the uses of fire in the following comprehensive sen- 
tence: “ Itis with fire,” says he, “that man prepares his food, 
that he dissolves metals, vitrifies rocks, hardens clay, softens 
iron, and gives to all the productions of the earth, the forms 
and combinations which his necessities require.” 
V. But our attention has been hitherto engrossed with con- 
templating the agencies of heat on the anorganized forms of 
