II.—PROGRESS OF GEOLOGY
The earth and its origin were much later than the heavens in becoming the object of scientific investigation. The numerous ancient and modern cosmogonies do, indeed, profess to give us as good an insight into the origin of the earth as into that of the heavens; but the mythological raiment, in which all alike are clothed, betrays their origin in poetic fancy. Among the countless legends of creation which we find in the history of religions and of thought there is one that soon took precedence of all the rest—the Mosaic story of creation as told in the first book of the Hexateuch. It did not exist in its present form until long after the death of Moses (probably not until eight hundred years afterwards); but its sources are much older, and are to be found for the most part in Assyrian, Babylonian, and Hindoo legends. This Hebrew legend of creation obtained its great influence through its adoption into the Christian faith and its consecration as the “Word of God.” Greek philosophers had already, five hundred years before Christ, explained the natural origin of the earth in the same way as that of other cosmic bodies. Xenophanes of Colophon had even recognized the true character of the fossils which were afterwards to prove of such moment; the great painter, Leonardo da Vinci, of the fifteenth century, also explained the fossils as the petrified remains of animals which had lived in earlier periods of the earth’s history. But the authority of the Bible, especially the myth of the deluge, prevented any further progress in this direction, and insured the triumph of the Mosaic legend until about the middle of the last century. It survives even at the present day among orthodox theologians. However, in the second half of the eighteenth century, scientific inquiry into the structure of the crust of the earth set to work independently of the Mosaic story, and it soon led to certain conclusions as to the origin of the earth. The founder of geology, Werner of Freiberg, thought that all the rocks were formed in water, while Voigt and Hutton (1788) rightly contended that only the stratified, fossil-bearing rocks had had an aquatic origin, and that the Vulcanic or Plutonic mountain ranges had been formed by the cooling down of molten matter.
The heated conflict of these “Neptunian” and “Plutonic” schools was still going on during the first three decades of the present century; it was only settled when Karl Hoff (1822) established the principle of “actualism,” and Sir Charles Lyell applied it with signal success to the entire natural evolution of the earth. The Principles of Geology of Lyell (1830) secured the full recognition of the supremely important theory of continuity in the formation of the earth’s crust, as opposed to the catastrophic theory of Cuvier.[34] Palæontology, which had been founded by Cuvier’s work on fossil bones (1812), was of the greatest service to geology; by the middle of the present century it had advanced so far that the chief periods in the history of the earth and its inhabitants could be established. The comparatively thin crust of the earth was now recognized with certainty to be the hard surface formed by the cooling of an incandescent fluid planet, which still continues its slow, unbroken course of refrigeration and condensation. The crumpling of the stiffened crust, “the reaction of the molten fiery contents on the cool surface,” and especially the unceasing geological action of water, are the natural causes which are daily at work in the secular formation of the crust of the earth and its mountains.
To the brilliant progress of modern geology we owe three extremely important results of general import. In the first place, it has excluded from the story of the earth all questions of miracle, all questions of supernatural agencies, in the building of the mountains and the shaping of the continents. In the second place, our idea of the length of the vast period of time which had been absorbed in their formation has been considerably enlarged. We now know that the huge mountains of the palæozoic, mesozoic, and cenozoic formations have taken, not thousands, but millions of years in their growth. In the third place, we now know that all the countless fossils that are found in those formations are not “sports of nature,” as was believed one hundred and fifty years ago, but the petrified remains of organisms that lived in earlier periods of the earth’s history, and arose by gradual transformation from a long series of ancestors.