280 Preface to The Natural History 
if the strata were consolidated and cemented by the heat and 
fusion cf subterraneous fire, all the strata, which have a tendency 
to, and may easily be hardened by fire, would be found in an in- 
durated state; but this in fact is not the case,—so far from it, 
that it is well known to every person who takes the least notice 
of these things, that we find in all countries great numbers of 
tilly and argillaceous strata, so very soft, that they differ little 
from a mere sediment from which the water has been pressed 
out, and which decomposes and falls to a mere sediment or clay, 
almost immediately upon being exposed to the external air. 
And it is remarkable, that these soft argillaceous strata are 
commonly situated immediately above and below very hard strata 
of indurated stone, upon which the external air has no sudden 
visible effect. How shall we account for this fact upon this hy-, 
pothesis? It cannot be pretended that these soft strata con- 
tain any marks or characters of being consolidated by the heat 
and fusion of fire; for they are not consolidated nor cemented 
at all, but only compressed by the superincumbent weight: of 
strata; nor can it be pretended, that they are not capable of 
being hardened by fire. ‘ 
In fact, we know the contrary by experience, as they are every 
day hardened in our open fires, and in proper kilns, for various 
purposes, and to various degrees of solidity and induration. If 
subterraneous fire had produced the solidity of our rocks, these 
soft substances would have been indurated, as well as their con- 
comitant strata, 
But these soft strata are a proof, that our rocks are cemented 
by a terrene, sparry, and siliceous fluid, which is, by degrees, 
inspissated and hardened by the pressing out or evaporation of 
superfluous moisture; and they also prove, that these argillaceous 
strata can only be consolidated and cemented by fire, which has 
not been applied to them. We can only select a few facts which 
oppose this system. The instances to be found in the book of 
nature are endless. 
JII. The third proposition which we are to consider in our 
author’s Theory of the Earth, viz. That the rocks and strata, . 
which were formed and consolidated beneath the waters of the 
ocean by subterraneous fire, were afterwards inflated and forced 
up from under water, by the expansive force of the same subier- 
raneous fire, to the height of our habitable earth, and of all the 
mountains upon the face of the globe, is an hypothesis as singular 
and extraordinary as the consolidation of strata beneath the wa- 
ters of the ocean by the heat and fusion of fire. 
Most of the operations and effects of subterraneous fire, that 
we have any knowledge of, are outrageously violent and destruc- 
tive, and.only produce disorder and ruin, If the bed of the 
ocean 
