“Eligat quis quod potest: tantum ne aliquid temere atque incognitum pro cognito asserat; memineritque se hominem de divinis operibus quantum permittitur quærere.”—De Genesi Liber Imperfectus, cap. ix., n. 80.
APPENDIX TO THE AMERICAN EDITION.
From Prof. J. D. Dana’s Manual of Geology. [8vo. Philadelphia: T. Bliss & Co.] By permission of the author.
COSMOGONY.
The science of cosmogony treats of the history of creation.
Geology comprises that later portion of the history which is within the range of direct investigation, beginning with the rock-covered globe, and gathering only a few hints as to a previous state of igneous fluidity.
Through Astronomy our knowledge of this earlier state becomes less doubtful, and we even discover evidence of a period still more remote. Ascertaining thence that the sun of our system is in intense ignition, that the moon, the earth’s satellite, was once a globe of fire, but is now cooled and covered with extinct craters, and that space is filled with burning suns,—and learning also from physical science that all heated bodies in space must have been losing heat through past time, the smallest most rapidly,—we safely conclude that the earth has passed through a stage of igneous fluidity.
Again, as to the remoter period: the forms of the nebulæ and of other starry systems in the heavens, and the relations which subsist between the spheres in our own system, have been found to be such as would have resulted if the whole universe had been evolved from an original nebula or gaseous fluid. It is not necessary for the strength of this argument that any portion of the primal nebula should exist now at this late period in the history of the universe: it is only what might have been expected that the nebulæ of the present heavens should be turning out to be clusters of stars. If, then, this nebular theory be true, the universe has been developed from a primal unit, and the earth is one of the individual orbs produced in the course of its evolution. Its history is in kind like that which has been deciphered with regard to the earth: it only carries the action of physical forces, under a sustaining and directing hand, further back in time.
The science also of Chemistry is aiding in the study of the earth’s earliest development, and is preparing itself to write a history of the various changes which should have taken place among the elements from the first commencement of combination to the formation of the solid crust of our globe.
It is not proposed to enter either into chemical or astronomical details in this place, but, supposing the nebular theory to be true, briefly to mention the great stages of progress in the history of the earth, or those successive periods which stand out prominently in time through the exhibition of some new idea in the grand system of progress. The views here offered, and the following on the cosmogony of the Bible, are essentially those brought out by Professor Guyot in his lectures.