Iron , 
241 
from making observations, and acquire no habit of detail- 
ing them. Others again, from their earliest infancy, 
have been accustomed to observe, that certain appearan- 
ces, time out of mind to them, had always followed cer- 
j! tain actions performed. They acquire a laconic habit of 
ii reasoning ; and if asked how such appearances are to be 
accounted for, their answer is, “ They must exist so and 
so — -it is in the very nature of the thing.” 
It is difficult to conceive a more ample field for obser- 
vation than an extensive foundry,, Combination, change s 
decomposition, combustion, and deflagration, are constant- 
ly performing their respective parts, and continually pre- 
senting matter under new and interesting appearances., 
Elementary substances, subject to no real change, are 
j modified in a variety of ways by the alternation of heat 
and cold. The laws which govern these are constantly 
exerted to produce effects equivalent to the exciting cause; 
and, while we often remain heedless spectators, these un- 
erring operations are productive of phenomena which 
frequently elude our sagacity or puzzle our judgment* 
The subject of contraction and expansion appears sim- 
ple, and the presence or absence of caloric alone in the 
body operated upon frequently explains, in a most satisfac- 
tory manner, the whole minutiae. 
But this regards only the heating of certain substances 
in temperatures short of fusing them. When the object 
of experiment is exposed to a heat sufficient to fuse it, 
it then becomes subject to new laws as a fluid, and exhi- 
bits phenomena entirely different. By not taking the 
change of state from that of a solid to afluid into the ac- 
count, some writers have given an awkward and unsatis- 
factory account of the laws which regulate iron in these 
two different states. Before I proceed to detail some ex- 
periments made upon this subject, I shall trace out the dif 
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