We have, first, Burnet's Theory of the Earth. This surely cannot be considered in any other light than as a dream, formed upon the poetic fiction of a golden age, and that of iron which had succeeded it; at the same time, there are certain appearances in the earth which would, in a partial view of things, seem to justify that imagination. In Telliamed, again, we have a very ingenious theory, with regard to the production of the earth above the surface of the sea, and of the origin of those land animals which now inhabit that earth. This is a theory which has something in it like a regular system, such as we might expect to find in nature; but, it is only a physical romance, and cannot be considered in a serious view, although apparently better founded than most of that which has been wrote upon the subject.
We have then a theory of a very different kind; this is that of the Count de Buffon. Here is a theory, not founded on any regular system, but upon an irregularity of nature, or an accident supposed to have happened to the sun. But, are we to consider as a theory of the earth, an accident by which a planetary body had been made to increase the number of these in the solar system? The circumvolution of a planetary body (allowing it to have happened in that manner) cannot form the system of a world, such as our earth exhibits; and, in forming a theory of the earth, it is required to see the aptitude of every part of this complicated machine to fulfil the purpose of its intention, and not to suppose the wise system of this world to have arisen from, the cooling of a lump of melted matter which had belonged to another body. When we consider the power and wisdom that must have been exerted in the contriving, creating, and maintaining this living world which sustains such a variety of plants and animals, the revolution of a mass of dead matter according to the laws of projectiles, although in perfect wisdom, is but like a unite among an infinite series of ascending numbers.
After the theory of that eloquent writer, founded on a mere accident, or rather the error of a comet which produced the beautiful system of this world, M. de Luc, in his Theory of the earth, has given us the history of a disaster which befell this well contrived world;—a disaster which caused the general deluge, and which, without a miracle, must have undone a system of living beings that are so well adapted to the present state of things. But, surely, general deluges form no part of the theory of the earth; for, the purpose of this earth is evidently to maintain vegetable and animal life, and not to destroy them.
Besides these imaginary great operations in the natural history of this earth, we have also certain suppositions of geologists and mineralists with regard to the effect of water, for explaining to us the consolidation of the loose materials of which the strata of the earth had been composed, and also for producing every other appearance, or any which shall happen to occur in the examination of the earth, and require to be explained. That this is no exaggerated representation, and that this is all we have as a theory, in the suppositions of those geologists, will appear from the following state of the case.
They suppose water the agent employed in forming the solid bodies of the earth, and in producing those crystallised bodies which appear in the mineral kingdom. That this is a mere supposition will appear by considering; first, that they do not know how this agent water is to operate in producing those effects; nor have they any direct proof of the fact which is alleged, from a very fallaceous analogy; and, secondly, that they cannot tell us where this operation is to be performed. They cannot say that it is in the earth above the level of the sea: for, the same appearances are found as deep as we can examine below that level; besides, we see that water has the opposite effect upon the surface of the earth, through which it percolates dissolving soluble substances, and thus resolving solid bodies in preparing soil for plants. If, again, it be below the level of the sea, that strata of the earth are supposed to be consolidated by the infiltration of that water which falls from the heavens; this cannot be allowed, so far as whatever of the earth is bibulous, in that place, must have been always full of water, consequently cannot admit of that supposed infiltration.
But allowing those suppositions to be true, there is nothing in them like a theory of the earth,—a theory that should bring the operations of the world into the regularity of ends and means, and, by generalizing these regular events, show us the operation of perfect intelligence forming a design; they are only an attempt to show how certain things, which we see, have happened without any perceivable design, or without any farther design than this particular effect which we perceive. If we believe that there is almighty power, and supreme wisdom employed for sustaining that beautiful system of plants and animals which is so interesting to us, we must certainly conclude, that the earth, on which this system of living things depends, has been constructed on principles that are adequate to the end proposed, and procure it a perfection which it is our business to explore. Therefore, a proper system of the earth should lead us to see that wise contraction, by which this earth is made to answer the purpose of its intention and to preserve itself from every accident by which the design of this living world might be frustrated as this world is an active scene. or a material machine moving in all its parts, we must see how this machine is so contrived, as either to have those parts to move without wearing and decay, or to have those parts, which are wasting and decaying, again repaired.
A rock or stone is not a subject that, of itself, may interest a philosopher to study; but, when he comes to see the necessity of those hard bodies, in the constitution of this earth, or for the permanency of the land on which we dwell, and when he finds that there are means wisely provided for the renovation of this necessary decaying part, as well as that of every other, he then, with pleasure, contemplates this manifestation of design, and thus connects the mineral system of this earth with that by which the heavenly bodies are made to move perpetually in their orbits. It is not, therefore, simply by seeing the concretion of mineral bodies that a philosopher is to be gratified in his his intellectual pursuit, but by the contemplation of that system in which the necessary resolution of this earth, while at present it serves the purpose of vegetation, or the fertility of our soil, is the very means employed in furnishing the materials of future land.
It is such a view as this that I have endeavoured to represent in the theory which I have given. I have there stated the present situation of things, by which we are led to perceive a former state; and, from that necessary progress of actual things, I have concluded a certain system according to which things will be changed, without any accident or error. It is by tracing this regular system in nature that a philosopher is to perceive the wisdom with which this world has been contrived; but, he must see that wisdom founded upon the aptitude of all the parts to fulfil the intention of the design; and that intention is to be deduced from the end which is known to be attained. Thus we are first to reason from effect to cause, in seeing the order of that which has already happened; and then, from those known causes, to reason forwards, so as to conceive that which is to come to pass in time. Such would be the philosophy of this earth, formed by the highest generalisation of phenomena, a generalisation which had required the particular investigation of inductive reasoning.
That no such theory as this, founded upon water as an agent operating in the changes of this earth, has yet appeared, will, I believe be easily allowed. With regard again to fire as an agent in the mineral operations of this earth, geologists have formed no consistent theory. They see volcanoes in all the quarters of the globe, and from those burning mountains, they conjecture other mountains have been formed. But a burning mountain is only a matter of fact; and, they have not on this formed any general principle, for establishing what may be called a theory of the earth. Those who have considered subterraneous fires as producing certain effects, neither know how these have been procured, nor do they see the proper purpose for which they are employed in the system of this world. In this case, the agent fire is only seen as a destructive element, in like manner as deluges of water have been attributed by others to changes which have happened in the natural state of things. These operations are seen only as the accidents of nature, and not as part of that design by which the earth, which is necessarily wasted in the operations of the world, is to be repaired.
So far from employing heat or subterraneous fire as an agent in the mineral operations of the earth, the volcanic philosophers do not even attempt to explain upon that principle the frequent nodules of calcareous, zeolite, and other spatose and agaty substances, in those basaltic bodies which they consider as lavas. Instead then of learning to see the operation of heat as a general principle of mineral consolidation and crystallization, the volcanic philosophers endeavour to explain those particular appearances, which they think inconsistent with fusion, by aqueous infiltration, no otherwise than other mineralists who do not admit the igneous origin of those basaltic bodies. Thus, that great agent, subterraneous heat, has never been employed by geologists, as a general principle in the theory of the earth; it has been only considered as an occasional circumstance, or as the accident of having certain mineral bodies, which are inflammable, kindled in the earth, without so much as seeing how that may be done.