reason without data is nothing but delusion. A
theory, therefore, which is limited to the actual constitution of this
earth, cannot be allowed to proceed one step beyond the present order of
things.

But, having surveyed the order of this living world, and having
investigated the progress of this active scene of life, death and
circulation, we find ample data on which to found a train of the most
conclusive reasoning with regard to a general design. It is thus that
there is to be perceived another system of active things for the
contemplation of our mind;--things which, though not immediately within
our view, are not the less certain in being out of our sight; and things
which must necessarily be comprehended in the theory of the earth, if we
are to give stability to it as a world sustaining plants and animals.
This is a mineral system, by which the decayed constitution of an earth,
or fruitful surface of habitable land, may be continually renewed in
proportion as it is wasted in the operations of this world.

It is in this mineral system that I have occasion to compare the
explanations, which I give of certain natural appearances, with the
theories or explanations which have been given by others, and which are
generally received as the proper theory of those mineral operations. I
am, therefore, to examine those different opinions, respecting the
means employed by nature for producing particular appearances in the
construction of our land, appearances which must be explained in some
consistent mineral theory.

These appearances may all be comprehended under two heads, which are now
to be mentioned, in order to see the importance of their explanation, or
purpose which such an explanation is to serve in a theory of the earth.
The first kind of these appearances is that of known bodies which we
find composing part of the masses of our land, bodies whose natural
history we know, as having existed in another state previous to the
composition of this earth where they now are found; these are the
relicts or parts of animal and vegetable bodies, and various stony
substances broken and worn by attrition, all which had belonged to a
former earth. By means of these known objects, we are to learn a great
deal of the natural history of this earth; and, it is in tracing that
history, from where we first perceive it, to the present state of
things, that forms the subject of a geological and mineralogical theory
of this earth. But,