370 Mr A. J. Avre on the Expansion of Stone 
this gradual increase in the length of the rod ; and by the effect 
of the two heatings noted after I observed it, the rod was length- 
ened .0096, or nearly the hundredth of an inch. On the rod of 
Carrara marble, the elongation took place mostly at the first heat- 
ing, and it amounted to .0135 of an inch. This may probably 
serve to account for the warping which sometimes takes place on 
those parts of chimney-pieces which are subjected to the greatest 
action of the fire. It is impossible to say how far this lengthen- 
ing would be increased by a greater change of temperature ; but, 
since Mr Bazzace has applied the expansion of stone to the ex- 
planation of geological phenomena, this property of limestone 
may also be taken into account, as it only requires the heat to 
have been once in action after the strata have been formed. In 
the experiment on the rod of Carrara marble, the whole effect 
was produced by an increase of temperature of 157° F.; and 
if we suppose this to have acted on strata five miles deep, the 
depth taken by Mr Bassace, in accounting for the changes 
of the level of the Temple of Serapis, the surface would have been 
raised by not less than 153 feet. Little weight, however, can be 
attached to such explanations of the great operations of nature, 
as there may be a vast difference between the effect of heat 
quickly communicated to the small pieces of stone on which we 
perform our experiments, and the necessarily slow diffusion of 
the heat through such a depth of strata as we have supposed. 
In order to ascertain if there was any connexion between the 
density of stones of the same composition and their expansibility, 
as takes place with the metals, I determined the specific gravity 
of several of the rods, but the one property does not appear to 
have the least dependence on the other. For instance, the spe- 
cific gravity of Sicilian white marble and Galway black marble 
is 2.7127 and 2.7093, almost exactly alike ; the expansion for 
180° F. of the former is .0325392, while that of the latter is 
only .0102394, not one-third of the first. In determining the 
