Intelligence and Miscellaneous Articles. 67 
I place in the different apparatus two spheres, one of caoutchouc 
and the other of bronze, which I assume are exactly identical, so 
as to simplify the reasoning; a few millimetres of pressure are 
sufficient to raise the water 300 divisions in the rod of the caout- 
chouc sphere ; in the other the motion of the meniscus is barely 
perceptible, and it cannot be measured with accuracy. It follows 
from this that (referring to the formula, which gives in this case the 
variation of the internal volume), whatever may be in the case of 
bronze the value’of « between zero and 3 (the accented letters refer 
to bronze), a is very great in reference to a’. 
It might be feared that in this case a considerable amount of the 
diminution of volume arises from a change of form; but this first 
operation might be replaced by a direct determination of a by 
means of traction; we obtain the same result. In one of my 
. a ° 
experiments -, was equal to 60,000 in round numbers. 
a 
That being so, let us compress internally and externally at the 
same time: according to the formula relative to this case, the 
changes of internal volume will be proportional to K and K’; 
K should therefore be very great in comparison with K’, the 
compressibility would even be relatively negligible, and the liquid 
should ascend in the stem of the caoutchouc sphere; but nothing 
of this kind takes place: the water sinks whatever be the pressure, 
and gives the inevitable irregularities with caoutchouc. It would be 
difficult to say whether the variation of volume has been greater 
with this body or for bronze, so small is the mean difference ; hence 
ais comparable to a’, and is perhaps even smaller. It evidently 
follows from this that the ratio (4) can only be satisfied provided 
that a = ° is very small, and therefore o very little different 
—A0 
from 4. 
Assuming for o’ the number 3, we have from the preceding 
K 1 
GB Re eR 
i 2( K’ * T80000 
Whatever errors may be attributed to want of homogeneity, to 
small deformations, and to permanent deformations, even if the 
results found were double, or even tenfold, it may be said that o 
would still be very little different from 34, and far higher for 
example than 0-499. 
We may, moreover, by means of general formule and without 
comparing caoutchouc to another body, arrive at the same conclusion 
in different ways, which essentially amount to this: the coefficient 
of cubical compressibility is very small, as actual experiment shows; 
as moreover it is equal to 3a(1—2c), and since a is very great, 
1—2o must be very small, and therefore o very near 4. 
There is nothing contradictory in this result. It follows from 
that and from the ratio (1) that » is very small; and therefore 
from ratio (3) that a is very great: this is in fact the case. 
But here a great difficulty presents itself. The various caout- 
