Geology . 425 
could no longer find fluid to hold them in solution, would 
crystallize. 
These last are alluvial deposits ; which also are suffici- 
ently general to merit the title of formations, although 
varying in their composition perpetually, as clay, loam ? 
marie, bog ore, sand, gravel, peat, &c. and their combi- 
nations. These occupy the lowest levels and the bases 
of the other rocks. 
Beside these, occasionally we meet with volcanic rocks 
or stones ; lavas. These contain debris or broken frag- 
ments of many deep formations, as the granite, mica slate, 
greenstone, hornblende, and sandstone found in ejected 
granular or primitive limestone. Hence some volcanic 
caverns are probably situated between the nucleus and 
the primitive strata : a situation which we are led to pre- 
sume, from the inclination or dip of the oldest formations : 
their position w 7 ould naturally have been level and hori- 
zontal, had not some mighty force raised them from their 
base. What effect the influence of the moon has had, in 
determining the circumstances of these earthy depositions 
out of the immense body of water that in their chaotic 
state contained them, no one now can fully explain : that 
it must have produced oceanic tides then, as well as now, 
perpetually varying, with the varying density of the mass 
of turbid fluid acted upon, we can hardly doubt. It is 
evident also that many ages must have passed before the 
surface of our globe, put off its chaotic state, and became 
fit for the habitation of man. The general system, of 
which I have presented a scanty outline, seems pointed out 
in most of its parts, by facts and appearances not to be 
denied, or by other theories so well explained : but as to 
all the particular s, doubts and uncertainties hang over 
them, which more accurate and future observations may 
in some degree serve to explain. 
