One of the basic principles of the science of geology Stensen taught as follows: "If a given body of definite form, produced according to the laws of nature, be carefully examined, it will show in itself the place and manner of its origin." This principle he showed would apply so comprehensively that the existence of many things, hitherto apparently inexplicable, became rather easy of solution. It must not be forgotten that before this time two explanations for the existence of peculiar bodies, or of ordinary bodies, in peculiar places, had been offered. According to one school of thought, the fossils found deep in the earth, or sometimes in the midst of rocks, had been created there. It was as if the creative force had run beyond the ordinary bounds of nature and had produced certain things, ordinarily associated with life, even in the midst of dead matter. The other explanation suggested was that the flood had in its work of destruction upon earth caused many anomalous displacements of living things, and had buried some of the {155} animals under such circumstances that later they were found even beneath rocks, or deep down in the earth, far beyond where the animals could be supposed to have penetrated by any ordinary means during life. Stensen had observed very faithfully the various strata that are to be found wherever special appearances of the earth's surface were exposed, or wherever deep excavations were made. His explanation of how these various strata are formed will serve to show, perhaps better than anything else, how far advanced he was in his realization of ideas that are supposed to belong only to modern geology. He said: "The powdery layers of the earth's surface must necessarily at some time have been held in suspension in water, from which they were precipitated by their own weight. The movement of the fluid scattered the precipitate here and there and gave to it a level surface." "Bodies of considerable circumference," Stensen continues, "which are found in the various layers of the earth, followed the laws of gravity as regards their position and their relations to one another. The powdery material of the earth's strata took on so completely the form of the bodies which it surrounded that even the smallest apertures became filled up and the powdery layer fitted accurately to the surface of the object and even took something of its polish." With regard to the composition of the various strata of the earth, the father of geology {156} considered that if in a layer of rock all the portions are of the same kind there is no reason to deny that such a layer came into existence at the time of creation, when the whole surface of the earth was covered with fluid. If, however, in any one stratum portions of another stratum are found, or if the remains of plants or animals occur, there is no doubt that such a stratum had not its origin at the time of creation, but came into existence later.