354 On th PROGRESS of HEAT 
“-fented as the grand excellence of the Huttonian Theory *.”’ 
“ Again, he obferves, in giving what he fays appears to him a 
demonftration of the fallacy of the firft principles of the Hut- - 
tonian Syftem, “ it will not be difputed, that the tendency of 
“ caloric is to diffufe itfelf over matter, till a common tempe- 
“ rature is eftablifhed. Nor will it probably be denied, that a 
“ power conftantly diffufing itfelf from the centre of any mafs 
“ of matter, cannot remain for an indefinite time locally accu- 
“ mulated in that mafs, but muft at length become equal or 
“ nearly fo over the whole f.”’ 
2. 1 muft confefs, notwithftanding the refpe& I entertain for 
the acutenefs and accuracy of the author of this reafoning, that 
it does not appear to me to poflefs the force which he afcribes to 
it; nor to be confiftent with many facts that fall every day un- 
der our obfervation. . A fire foon heats a room to a certain de- 
gree, and though kept up ever fo long, if its intenfity, and all 
other circumftances remain the fame, the heat continues very 
unequally diftributed through the room ; but the temperature 
of every part continues invariable. If a bar of iron has one 
end of it thruft into the fire, the other end will not in any 
length: of time become red-hot; but the whole bar will quick- 
ly come into fuch a ftate, that every point will have a fixed 
temperature, lower as it is farther from the fire, but remain- 
ing invariable while the condition of the fire, and of the 
medium that furrounds the bar, continues the fame. The 
reafon indeed is plain: the equilibrium of heat is not fo much 
a primary law in the diftribution of that fluid, as the limitation 
of another law which is general and ultimate, confifting in the 
tendency of heat to pafs with a greater or a lefs velocity, 
according to circumftances, from bodies where the temperature 
is 
* Murray's Syflem of Chemistry, vol. iii. Appendix, p. 49. 
+ Page 51. 
