and Folcanic Substances. 207 
nation that we at present possess ; all others are conjectural 
ony 3 without foundation in known facts. 
o enable us therefore to explain, any geological phe- 
nomenon whose cause is doubtful and obscure, we must ac- 
cumulate and review the known facts that are manifestly 
connected with water as the agent; and also the known 
facts that are manifestly connected with fire as the agent ; 
and apply the indubitable and the probable conclusions 
which these facts afford us, to any case of difficulty presen- 
ted for our examination. 
There are only three ways within our knowledge in which 
water can have acted upon the stones and earth that form 
the crust of the globe. 
1. By dissolving them. 
2. By sus ing them. wetewatn t : 
3. In torrents and in floods, by removing masses of rock 
from one place to another, 
ft may be assumed, that 
Earth forms not quite 1, and water 2 of the surface of the 
globe : look at any general map of the globe with this view. 
Taking the average depth of the sea, with La Place, at 
twelve miles, it will not suffice as a solvent of the primitive 
strata alone. : Richmond to Charlottes- 
ville in Virginia, at the foot of the south mountain with Mr. 
Vanuxem, a distance of seventy miles and upwards, it ap- 
peared to that gentleman and me, that we travelled over the 
edges of the primitive all the way till we came to the transi- 
tion country. We had not an opportunity of taking the an- 
gles made by the strata respectively with the horizon, but 
we can hardly be much beyond the fact in stating the low- 
est depth of the primitive there, at fifty miles. But the 
mineral substances of which the strata of the earth are com- 
posed, are upon the average nearly three times the weight 
of water under equal bulks. 
Further, to make a chemical solution of the earths as 
they are usually found in combination, as alumine, in clay 
late, mica, and slate clay : Lime, in carbonat, sulphat, and 
fluat, of Lime: Silex in quartz, hornstone, agate, &c. Ba- 
’y’es and strontian in their carbonats and sulphats : Magne- 
“in soap stone, serpentine, and chlorite : Zircon, in the 
acinth | Zirconite, and Jargon: Glucine in the Emerald : 
. 
ja, in the Yttriolite—will require upon the average seven 
