Hutton's _Theory of the Earth_ appeared in 1785, and in a more developed state, as a separate work, in 1795.[74] "The ruins of an older world," he said, "are visible in the present structure of our planet, and the strata which now compose our continents have been once beneath the sea, and were formed out of the waste of preëxisting continents. The same forces are still destroying, by chemical decomposition or mechanical violence, even the hardest rocks, and transporting the materials to the sea, where they are spread out and form strata analogous to those of more ancient date. Although loosely deposited along the bottom of the ocean, they became afterwards altered and consolidated by volcanic heat, and were then heaved up, fractured, and contorted." Again he said: "In the economy of the world I can find no traces of a beginning, no prospect of an end." As Lyell remarks: "Hutton imagined that the continents were first gradually destroyed by aqueous degradation, and when their ruins had furnished materials for new continents, they were upheaved by violent convulsions. He therefore required alternate periods of general disturbance and repose." To Hutton, therefore, we are indebted for the idea of the immensity of the duration of time. He was the forerunner of Lyell and of the uniformitarian school of geologists. Hutton observed that fossils characterized certain strata, but the value of fossils as time-marks and the principle of the superposition of stratified fossiliferous rocks were still more clearly established by William Smith, an English surveyor, in 1790. Meanwhile the Abbé Haüy, the founder of crystallography, was in 1802 Professor of Mineralogy in the Jardin des Plantes. _Lamarck's Contributions to Physical Geology; his Theory of the Earth._ Such were the amount and kind of knowledge regarding the origin and structure of our earth which existed at the close of the eighteenth century, while Lamarck was meditating his _Hydrogéologie_, and had begun to study the invertebrate fossils of the Paris tertiary basin. His object, he says in his work, is to present certain considerations which he believed to be new and of the first order, which had escaped the notice of physicists, and which seemed to him should serve as the foundations for a good theory of the earth. His theses are: 1. What are the natural consequences of the influence and the movements of the waters on the surface of the globe? 2. Why does the sea constantly occupy a basin within the limits which contain it, and there separate the dry parts of the surface of the globe always projecting above it? 3. Has the ocean basin always existed where we actually see it, and if we find proofs of the sojourn of the sea in places where it no longer remains, by what cause was it found there, and why is it no longer there?