357 
on some of the leading doctrines of caloric , &c. 
At 2 66° Fahr. which corresponds to 130° centigrade, I 
make it from Biot’s first formula 77.053, while at 130° by 
M. Pouillet, it is 75.68 ;* difference 1.973. Finally, 
At the temperature of 31 2°, f = 100 
100 a = 0.854121972 
10.000 h = — 0.208109100 
1000000 c = + 0.005800000 
0.651812872 
1.477121300 
Log. of = 2.128934172 F /= =F ioo = 134.57 
Experiment gives 167.00 
Mr. Dalton’s table 125.85 
The difference between experiment, and both calculations, 
is now excessive, and even between the two latter it amounts 
to nearly 9 inches. 
From this ample investigation, we may legitimately con- 
clude, that we ought to receive such geometrical representa- 
tions with great caution. M. Biot, indeed, with a candour 
becoming his genius, admits these formulas to be merely 
tentative approximations. The high reputation of this 
philosopher, and the geometrical skill here displayed, might 
have led the scientific world to repose confidence in his for- 
mula, within the limits of 55^ degrees centigrade = 100 
Fahr. It was therefore entitled to a deliberate examination. 
It is curious to observe that my very simple formula, 
Log. F = Log. 28.9 + n. Log. r, gives good approximations, 
* 1 30° centigr. gives by M. P. force of vapour — 1907.07 millemetres, of which 
taking *5.4 to the English inch, we have = 75.0S as above. 
2 5-4 
