24 Sir C. Lyell on the Mineral Waters of Bath. 
their way into the regions of subterranean heat. But the exist- 
ence of water under great pressure affords no argument against 
our attributing an excessively high temperature to the mass with — 
which it is mixed up. Still less does the point to which the 
melted matter must be cooled down before it consolidates or — 
crystallizes into lava or granite afford any test of the degree of — 
heat which the same matter must have acquired when it was 
melted and made to form lakes and seas in the interior of the — 
and yet possess a heat of 120° Centigrade, or 248° F. 
then, may not the temperature of such water be at the depth : 
of a few thousand feet? It might soon attain a white heat un- ’ 
der pressure; and as to lava, they who have beheld it issue, as 4 
I did in 1858, from the southwestern flanks of Vesuvius, with — 
a surface white and glowing like that of the san, and who have 
felt the scorching heat which it radiates, will form a high con- ~ 
ception of the intense temperature of the same lava at the bot- : 
tom of a vertical column several miles high, and communica: © 
ting with a great reservoir of fused matter, which, if it were to — 
begin at once to cool down, and were never to receive future ac: 
cessions of heat, might require a whole geological period before — 
it solidified. Of such slow refrigeration, hot springs may 4 
among the most effective instruments, abstracting slowly from — 
the subterranean molten mass that heat which clouds of vapor — 
are seen to carry off in a latent form from a volcanic crater dur- — 
ing an eruption, or from a lava-stream during its solidification. — 
It is more than forty years since Mr. Scrope, in his work on vol- 
canos, insisted on the important part which water plays in au _ 
eruption, when intimately mixed up with the component mate- — 
rials of lava, aiding as he supposed, in giving mobility to the 
more solid materials of the fluid mass. But, when advocating — 
this igneo-aqueous theory, he never dreamed of impugning the — 
Huttonian doctrine as to the intensity of heat which the produc: _ 
tion of the unstratified rocks, those of the plutonic class espe- — 
. . 
cially, implies. 
yut_the necessity of our appealing to an original 
central heat, or the igneous fluidity of the earth’s nucleus. © 
