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OBSERVATIONS ON THE NATURE OF HEAT. 245 
cooling from 40° to 32°, Fah., expands: but this is accounted for on 
a different principle. It is generally supposed that the crystals 
which are formed on the water becoming ice, observe a particular 
arrangement, or that the coaptation among them is not such as to 
occupy the least possible space. Were this law otherwise, the lakes 
and streams, in severe winters, particularly in northern regions, 
would be rendered one complete mass of ice; in short, the fountains 
of the deep would be dried up, and man would have only a precarious 
supply of this indispensable requisite. But as it is, water, on cooling 
from 40° to 32°, expands ; it therefore becomes lighter, and swims 
above the heavier. The particular arrangement of the crystals, as 
already mentioned, will explain the enlargement without the seeming 
paradox of matter becoming larger, or matter being extracted. 
The only other comparison which I shall draw between the two 
hypotheses is derived from the production of calorie by percussion or 
friction; and this, I may add, is reckoned by some as one of the 
greatest stumblingblocks to the idea that caloric is material. 
They argue that whatever can be generated out of nothing cannot 
be material. Thus, Dr. Young, in his Lectures on Natural Philo- 
sophy, says, “If the heat is neither received from the surrounding 
bodies (which it cannot be without a depression of their temperature), 
nor derived from the quantity already accumulated in the bodies 
themselves (which it could not be, even if their capacities were dimi- 
nished in any imaginable degree), there is no alternative but to allow 
that heat must be actually generated by friction ; and if it is gene- 
rated out of nothing it cannot be matter, nor even an immaterial or 
semi material substance.” The first of these propositions is admitted, 
as it can bear the test of experiment; but the second is a mere as- 
sumption, viz., “ that the caloric cannot be derived from the quantity 
already accumulated in the bodies themselves, even if their capacities 
were diminished.” Were we able to measure the quantity of caloric 
in any body, this supposition might be entertained in preference to 
one more in accordance with the laws of matter. This, however, we 
cannot do, with our present information ; for any body may contain 
one degree of caloric, or ten thousand, as our knowledge is only re- 
lative. Further, the reverse of this assumption will explain all the 
phenomena attendant on percussion or friction, without the violation 
of a single law of physics. Whereas the idea that caloric is merely 
the consequence of motion, for the support of which the assumption 
is raised, can only be defended by setting aside an important fact in 
