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44 : a ek Dr. John Garric on the 
ona larger scale than it has _ heretofore examined ; anda 
an object in view sufficiently valuable to justify the nek - 
of money for adequate machinery, and of time for a long series 
of careful and precise observations. Experiments on a sme 
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what is the actual result of large operations. And besides being 
a scale of suitable magnitude, they cannot be made accu- 
on 
rately by rude iad unskillful hands; they must be performed by. 
persons qualified by knowledge and practice to conduct them — 
through all the circumstances which a great range of ana 
ture, and a variety of degrees of condensation may prese By 
conjoining expectations of pecuniary profit with iilaeath at 
views, it — been placed in my power to fulfill these conditions, 
an ong course of expensive experiments, amidst much 
embarranaiient of many kinds, to elicit a near approach to truth. 
A portion of the money expended in conducting these experi- 
ments, was furnished by some commercial gentlemen of the city 
of New Orléhns. 
As the object of these gentlemen, in advancing sheit. ee 
was pecuniary gain, and this depended upon the quantity of hea 
absorbed, or in other words, the quantity of cold produced, st 
its applicability to the manufacture of ice, from the expansion of 
r its condensation, I was constrained to pay as much, per- 
tap more attention to the evolution of this effect a to the 
quantity of heat disengaged by the condensation. Two series 
of experiments were thus carried on at the same time, and each 
was made to act as a check upon the accuracy of the other; 
while no labor or care was spared to render both accurate. ‘To 
se experiments, a large and powerful machine has been 
constructed, planned for measuring alike the heat developed by 
condensation, and the heat absorbed by rarefaction of any volume 
of air—from two cubic feet to two thousand cubic yards or more, 
and under any degree of condensation from two to eight atmos- 
pheres. By operating with such masses o of air, the errors into 
which a experimenters had fallen, have been, in a grea 
measure a d. 
In the aaiee article I propose to give an account of the quan- 
tity of heat evolved by the condensation of air under a compress- 
ing force of from two up to eight atmospheres consecutively ; 
and in a succeeding number of this Journal to show the quan- 
tity absorbed by the expansion of the same air from a tension 
of two, four, and eight atmospheres, to the ordinary atmospheric 
. pressure. 
The machine, already mentioned as constructed, was intended 
for iensseg alike the heat evolved by the condensation of ait, 
e heat absorbed by its subsequent expansion. ‘The portion 
he 
