214 On the Capacity for Heat. 
mosphere, and of surrounding bodies upon the apparatus, while 
the experiment is going on, the quantity ofwater in the vessel 
is regulated so as to keep the bottle wholly submerged ‘in the 
liquid, and even the upper end of the neck covered, when the 
bottle is immersed. The vessel which contains this water is 
placed and suspended by a ring of cork in another vessel larger 
and higher, and the interval between the two is filled with eider 
down. 
The form of the bottle is such that its horizontal section pre- 
sents the figure of a rectangular cross. Some idea may be 
conceived of its form and dimensions, if we suppose a square 
piece of stick, each facet of which is four lines broad by four 
inches three lines in length, upon the four faces of which we 
have fixed four sticks of the same length (7.e. 4 inches 3 lines) 
but each of them being four lines thick by eight broad. 
The four sticks last described will exhibit the figure of the 
bottle: for the square piece of stick will be concealed by them 
from our view. 
The neck of the bottle is in the prolongation of its axis: if 
is four lines diameter by four high: it ought to be circular: the 
cork should be an inch long, and the bottle weigh 76°07 grammes 
without its cork. 
The cylindrical vase which contains the water is two inches 
diameter, and four inches nine lines high, and it weighs 74:65 
grammes. 
The exterior vessel in which the latter is suspended by the cork 
ring, is five inches three lines high and three inches diameter, so 
that the sides and bottom are every where separated by an interval 
of six lines: this interval is filled with eider down as already 
mentioned. 
To prevent the water from touching the eider down, the cork 
ring is covered with a thin coating of mastic. 
In order to ascertain the temperature of the bottle, and of the 
liquid which it contains, without being obliged to plunge a ther- 
mometer into the bottle, which would in this case be mecon- 
venient, I employed a very simple method. 
J placed a large bucket filled with water in a room with a 
northern aspect : I allowed it to assume the temperature of the 
rooni, taking care to shut the door and windows day and night. 
I placed the smail bottle on a stand in this bucket, keeping the 
upper part of the cork only out of the water. As the bottle is 
small and has a large surface, it speedily acquires the temperature 
of the bucket of water, but in order to be well convinced that 
the bottle and the liquid which it contains have acquired the 
temperature in question, I leave the bottle a considerable time 
in the bucket, frequently half an hour and sometimes more. 
In 
ee 
