606 On ‘the Materiality of Calorze. 
been complete, still the supply of ‘caloric could 
not thus be’ entirely cut off; simce’ it “hasbeen 
shewn ‘by ‘Count ‘Rumford, that “caloric: passes 
even through a torricellian vacuum: ’ Tf, there- 
fore; ‘friction’ produce ‘in 'bédies*some | ehange, 
which enables them’ to ‘attract caloric from/sur- 
rounding ‘substances, « this attraction may be 
equally efficient “in anvexhausted’ receiver,” as 
inone' containing’ an' atmosphere of mean‘den- 
sity. It would ‘be an’ interésting subject’ of 
experiment, ‘to ‘determine the ‘influence (of ‘at+ 
mospheres of ‘various densitiés,.as conductors ‘of 
caloric; for, since effects are proportionate to 
their causes; and it is ascertained that common 
air conducts caloric, better than it is conveyed 
through a vacuum, as 1000 is to 702, it may 
be expected that the ratio will hold in all inter- 
mediate degrees. 
In ‘Count Rumford’s masterly experiment, 
the metal, submitted to friction, was encom- 
passed by water; and air was’ carefully excluded 
from \the surfaces in motion. “Yet! the «water 
became hot, and -was' kept ‘boiling a consider- 
able time. In this-case, the only obvious'source 
of caloric, from without, was-through the’borer, 
employedin producing'the friction ; if it be-true, 
as the-Count has observed, that the water eculd 
mot, at the same instant, ‘be in the act ‘of ‘giving 
out and receiving heat. The same objection 
