he earth, we shall find
that such earth-knowledge--if I may so translate the word
geology--falls into the same categories.

"What is termed stratigraphical geology is neither more nor less
than the anatomy of the earth; and the history of the succession
of the formations is a history of the succession of such
anatomies, or corresponds with development, as distinct from
generation.

"The internal heat of the earth, the elevation and depression of
its crust, its belching forth of vapours, ashes, and lava, are
its activities, in as strict a sense as are warmth and the
movements and products of respiration the activities of an
animal. The phenomena of the seasons, of the trade-winds, of the
Gulf Stream, are as much the results of the reaction between
these inner activities and outward forces, as are the budding of
the leaves in spring, and their falling in autumn the effects of
the interaction between the organisation of a plant and the solar
light and heat. And, as the study of the activities of the living
being is called its physiology, so are these phenomena the
subject matter of an analogous telluric physiology, to which we
sometimes give the name of meteorology; sometimes of physical
geography, sometimes that of geology. Again, the earth has a
place in space and time, and relations to other bodies in both
these respects, which constitute its distribution. This subject
is usually left to the astronomer; but a knowledge of its broad
outlines seems to me to be an essential constituent of the stock
of geological ideas.

"All that can be ascertained concerning the structure,
succession of conditions, actions, and position in space of the
earth, is the matter of its natural history. But, as in Biology,
there remains the matter of reasoning from these facts to their
causes, which is just as much science as the other, and indeed
more; and this constitutes geological aetiology.

"Having regard to this general scheme of geological knowledge
and thought, it is obvious that geological speculation may be, so
to speak, anatomical and developmental speculation, so far as it
relates to points of stratigraphical arrangement which are out of
reach of direct observation; or, it may be physiological
speculation so far as it relates to undeterm