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Propagation of Heat in Fluids. 363 
been melted, but it was no. way affected by the vicinity of 
the hot iron. The intention im making the fheath project 
+ below the cylinder was to prevent internal motions in 
the oil, the particles of which, by becoming {pecifically 
lighter by being in contaét with the iron cylinder, would 
otherwife have {lid from under it and afcended. 
A fimilar experiment was tried with mercury poured to the 
- height of 1 inch oyer the ice, inftead of the 3 inches of oil, 
and the refult was exadtly the fame; though the ice at the 
time-could not bear a finger to touch it (by putting it down 
through the mercury), however expeditioufly removed, with~ 
out a portion being diffolved, and which inftantly became 
yifible on the bright furface of the mercury. 
. From his experiments the author feems inclined to doubt 
the exiftence of that peculiar kind of attraGion of predilec- 
tion which has been called chemical affinity, and to attri- 
bute the equal distribution of the particles of any body in its 
menfruum to the internal motions among the particles of 
the fluid occafioned by accidental changes of temperature, 
produced by the union of the two; or to a great difference 
in the fpecific gravity of the menftruum in its natural itate, 
and that of the fame fluid after it has been changed to a 
faturated folution. The following experiment ferves to fup- 
portthe author’s opinion: bape ; 
A cylindrical glafs jar was placed within a larger one 
which ftood ina fhallow earthen difh, nearly filled with 
pounded i¢e and water.. Ice cold frefh water, lightly tinged _ 
of a red colour with turnfol, was poured into the {mall jar 
to the height of 2 inches; and then, by means.of a funnel, 
which ended in a long and narrow tube, put down through 
that water and refting on the bottom of the jar, an equal 
quantity of the firongeft brine that could be made with fea- 
falt was poured in, fo gently that, without difturbing the 
freth water, the brine took the lower ftation, the coloured 
water repofing aboye it without the fmalleft appearance of 
blending. 
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