I caused ten bullets to be made of forged and beaten iron; the first,
of half-inch diameter; the second, of an inch; and soon progressively
to five inches: and as all the bullets were made of iron of the same
forge, their weights were found nearly proportionable to their volumes.
The bullet of half an inch weighed 190 grains, Paris weight; that of
an inch, 1522 grains; that of an inch and a half, 5136 grains; that of
two inches, 12173 grains; that of two inches and an half, 23781 grains;
that of three inches, 41085 grains; that of three inches and a half,
65254 grains; that of four inches, 97388 grains; that of four inches
and an half, 138179 grains; and that of five inches, 190211 grains. All
these weights were taken with very good scales, and those bullets which
were found too heavy, were filed.
While these bullets were making, the thermometer exposed to the open
air was at the freezing point, or some degrees below; but in the pit
where the bullets were suffered to cool, the thermometer was nearly ten
degrees above that point; that is to say, to the degree of temperature
of the pits of the observatory, and it is this degree which I have here
taken for that of the actual temperature of the earth. To know the
exact moment of their cooling to this actual temperature, other bullets
of the same matters, diameters, and not heated, were made use of for
comparison, and which were felt at the same time as the others. By the
immediate touch of the hand, or two hands, on the two bullets, we could
judge of the moment when they were equally cold; and as the greater or
less smoothness or roughness of bodies makes a great difference to the
touch; (a smooth body, whether hot or cold, appearing much more so than
a rough body, even of the same matter, although they are both equally
so) I took care that the cold bullets were rough, and like those
which had been heated, whose surfaces were sprinkled over with little
eminences produced by the fire.