Page:A Treatise on Geology, volume 2.djvu/295

 CHAP. X. immortal works we beg to direct the attention of those inconsiderate persons who think to advance Christianity by denying philosophy, and to confirm revelation by making its very truth depend upon their own narrow interpretations of nature.

Lest, however, we should fall into as great absurdities of another kind as these we have mentioned, it will be prudent to determine, if possible, the true character of a general theory of the earth; for in this there is a great liability to error. Geology, regarded as a body of facts, comprises not exclusively, nor specially, the phenomena which are now, or have been at any one former time, in progress on and within the earth, but embraces the whole succession of these occurrences, from the earliest operation of natural laws on the globe to the present hour. Each of the phenomena, taken singly, is the subject of interpretation by some special branch of natural science: the characters of organic fossils are referred to the zoologist and botanist; mineral compounds are examined chemically and crystallographically; the fractured crust of the earth receives explanation from the application of mechanical philosophy. The general view of these and other phenomena, manifested at one epoch, or during one period, and the survey of the condition of the globe at several such periods, are the proper objects of geological observation; and the successive states of the globe being thus ascertained, it is the business of inductive philosophy to discover the general antecedent condition or proximate cause upon which these successive states depend. If the research be successful, the result is a general theory of the earth; that is to say, a sufficient natural cause is found to explain, in combination with other agencies really existing, all the characteristic changes which have been observed in the earth's condition, in the degree, combination, and sequence which actually belong to them.

Perhaps an illustration may be usefully taken from exact science. la mathematical inquiries, a particular