70 Dr Boue's Observations on M. Beudanfs Opinions 
have an equal right to doubt the mechanical origin of cl ay -slate, 
grey-wacke, and even of some red sandstones, because we but 
seldom see their analogous rocks formed in the modern alluvium. 
The same reasoning might also be extended to the limestones of 
various epochs ; and, in this case, we instantly perceive the er- 
roneous nature of die conclusions to which this mode of pro- 
ceeding would lead us. 
Besides, why should we not employ, in the explanation of 
the differences of igneous deposits of very different ages, the 
same causes with which the Neptunists explain so well the varia- 
tion of the aggregated products of very different epochs ? Why 
should not the difference in age be taken into account in the 
first as well as in the last case, and be considered as capable of 
accounting for igneous as for Neptunian anomalies ? Is it in- 
consistent v/ith reason to suppose the laws of Nature as constant 
in their operations upon the terrestrial globe as in the heavens ; 
or is it more conformable with reason to adopt this immutability 
for a certain class of phenomena, namely for the aqueous, me- 
chanical, and chemical deposits ; and to believe that, at a deter- 
mined period, the volcanic formations have begun all of a sud- 
den, and continued till now, while previous to that period no- 
thing similar existed upon our planet, as none of the agents of 
these tremendous eruptions had been yet created ? I cannot 
believe that a Neptunist could have conceived an idea so con- 
trary to all natural analogy ; and how absurd would not he find 
the person, who should contend that the alluvial deposits have 
begun only since the appearance of Adam and Eve on the sur- 
face of the earth ? I am more inclined to suppose that my an- 
tagonists have not sufficiently considered this important ques- 
tion, that they have even neglected it, or vaguely resolved it, by 
imagining that perhaps the volcanic agents produced in those re- 
mote times, produced effects very diflbrent from those which the}^ 
now produce. If this be the case, I shall readily agree with 
those who entertain such an opinion, for all that will then be 
necessary, is to determine what is meant by the terms volcanic 
agents^ volcanoes^ igneous apertures^ volcanic and igneous pro- 
ducts. 
I would rather believe, that, after some reflection, both parties 
wiD agree in seeing the globe regulated, from the period of its 
