89 
and the Mode of its Communication. 
the air, =44°, in which 4 he instrument was cooled,) it will 
turn out, 8 minutes and 55 seconds after n h 30 min. The ob- 
served time was n h 39 minutes; which differs from the com- 
puted time no more than 5 seconds. 
If it were strictly true, as a very great philosopher and mathe- 
matician has advanced, that the velocity with which a hot body 
exposed to cool in a cold fluid medium parts with its heat, is as 
the difference of the temperatures of the body and of the me- 
dium, it is most certain, that the curve PQ could be no other 
than the logarithmic curve. Perhaps it may be so in fact, and 
that the variations from it which my experiments indicated, were 
owing solely to the imperfection of the divisions of our thermo- 
meters. If it be so, it is not impossible to divide the scale of 
a thermometer in such a manner as to indicate with certainty 
equal increments of heat, as thermometers ought to do ; but this 
is not the proper place to enlarge on this subject. I may perhaps 
return to it hereafter. 
Passing over in silence, a number of experiments I made 
in order to get thoroughly acquainted with my new instru- 
ments, and to assure myself that the results of similar ex- 
periments made with them were uniform, and might be de- 
pended on, I shall now proceed to give an account of several 
experiments made with pointed views, the results of some of 
which were very interesting. 
Experiment No. 1. The large cylindrical vessel No. 1, with its 
ends covered with warm clothing, in the manner before described, 
and its vertical sides (which were polished, and very clean and 
bright) exposed naked to the air, was filled with water nearly 
boiling hot, and placed on its wooden stand, on a table, in a 
mdccciv. N 
