94 New experimental Researches 
that we ought to receive such geometrical representations wita 
great caution. M. Biot, indeed, with a candour becoming his 
genius, admits these formule to be merely tentative approxima- 
tions. The high reputation of this philosopher, and the geo- 
metrical skill here displayed, might have led the scientific world 
to repose confidence in his formula, within the limits of 554 de- 
grees centigrade =100 Fahr. It was therefore entitled to a de- 
liberate examination. 
It is curious to observe that my very simple formula, Log. 
F = Log. 28:9 + n. Log. r, gives good approximations, through 
a much more extensive range, than the elaborate formula of the 
distinguished French geometer. Even when carried so high as 
the 310th degree of Fahr., we have 
Log. 28:9 + n. log. r = 2°19810=L, Fio93 hence 
F oo = 157°8. 4 
Experiment gives 161°3, a difference of only 34 inches at this 
prodigious elasticity; which may be deemed altogether unim- 
portant in practice. 
Biot’s formula gives a result 31 inches, and Mr. Dalton’s 40 
in defect. 
Of Professor Robison’s higher numbers, it is merely necessary 
to examine the successive differences for every 10° above 212°. 
These are 7:2, 8:9, 10°2, 11:9, 13°5, 13-8, 11-8, and the se- 
cond differences are + 1°7+1°341:7+1:6+0:3—2:0. 
Such striking irregularities cannot exist in the progression of 
nature. Betancourt’s are liable to a similar censure. We may 
find indeed small discrepancies in the best observations at such 
temperatures. 
§ Il. Experiments to determine the elastic Forces of the Va- 
pours of Alcohol, Ether, Oil of Turpentine, and Petroleum or 
Naphtha. 
The determination of the elasticities of these vapours is a very 
interesting problem in chemical philosophy. It may possibly 
unfold the law which connects temperature and elastic energy, 
and it may furnish likewise some useful applications. 
Mr. Dalton has examined the subject with considerable care. 
My experiments were performed with the apparatus above de- 
scribed, and were verified by frequent repetitions. The following 
results were noted down during the progress of the experiments. 
TABLE 
