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 Abbe Hauey, 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 _Hydrogeologie_, 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.