DEVELOPMENT OF GEOLOGY AS A SCIENCE.
Probably the earliest geologic phenomena to cause comment were earthquakes, active vol canoes and floods. These were the cause of fruitful, if unscientific, conjecture among the earliest peoples who were wont to ascribe them to the vagaries of mythological monsters. Aristotle believed earthquakes were due to sub terranean winds, and recognized a relation be tween them and volcanoes. Strabo followed in the same belief and going further was able to show the true nature of long dormant or ex tinct volcanoes. As early as the 6th century B.C. the presence of marine shells far inland was pointed to as an evidence that the land had been elevated from beneath the sea. Somewhat later it was affirmed that rivers eroded valleys and that land emerged from the ocean and was again resubmerged with exceeding slow ness.
But these advanced ideas took little hold upon the mind of the time and during the Middle Ages the dominance of the Church with its insistent adherence to the exact letter of the biblical story of creation was a strongly deterrent factor in the growth of all scientific thought. The presence of fossils in the rocks was ascribed by some to Noah's flood. Others seriously taught that the Creator made many unsuccessful attempts before the right forms were finally produced, and that fossils were these rejected forms. Others even insisted that fossils were made by the devil to perplex the faithful.
Nicholas Steno (1631-1687) was one of the earliest observers to work out consistent geo logical theories. He developed the idea of the marine nature of fossils and showed evidences that the stratified rocks in which they occur are similar to marine sediments now accumu lating. He advanced the idea that these rocks, where not now horizontal, must have undergone upheaval and deformation, and cited such fold ing as one of the chief causes' of mountains. Steno had followers, but at best his ideas gained ground slowly.
Many wildly fanciful speculations have been advanced to account for the origin of the earth, but the first serious scientific attempt was made by Descartes about 1644. He conceived the earth to have been at one time a molten mass like the sun, which cooled down to the con dition of a molten center with a solid crust.
Thus he laid down the foundation of the now famous nebular hypothesis.
Guettard (1715-1786) was the first to make geologic maps showing the distribution of vari ous rock formations and mineral deposits. He also did much to systematize paleontology. He published a work on the erosional effects of running water, citing many specific instances of its efficacy; suggested that the salinity of the sea was due to salts carried to it from the erosion of the land; and was the first to recog nize the true nature of the group of extinct volcanoes in Auvergne.
In 1763 Desmarest, a Frenchman, made a careful study of the basalts of Auvergne, and by noting their intimate association with vol canic scoria became convinced of their volcanic origin. In this belief he was strongly opposed by Werner (1749-1817), professor of mineralogy and mining at the Freiberg Mining Academy, who was probably the first to attempt to work out a stratigraphic classification of the formations of the earth's crust, which he be lieved could be applied everywhere. It is essen tially as follows: There existed a universal ocean from which the oldest or Primitive Rocks were chemically precipitated. As the earliest formations in the regions studied by him were granites, gneisses, basalts and other crystalline rocks, he assumed that these were of chemical origin. As the land gradually emerged from the universal ocean, erosion progressed and the Transition Rocks were mixtures of mechanical sediments with the Primitive series. As the waters became still further restricted mechani cal deposits predominated to which he gave the name Floetz Rocks. These in turn were fol lowed by the Alluvial series or recent clays, sands and gravels. He maintained strongly the chemical origin of basalts, as did his followers, and around him grew up a school known as the Neptunists, who vigorously argued his be liefs. The adherents of the igneous origin of basalt were also organized into a school under the name of the Plutonists and the controversy between them was for many years a bitter one. Though Werner was an enthusiast, his rigid ad herence to his own doctrines in the face of • evidence to the contrary probably did' much to retard real geologic advance.