100 LAMARCK, HIS LIFE AND WORK 
continents, they were upheaved by violent convul- 
sions. 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 Hatiy,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 re- 
garding the origin and structure of our earth which 
existed at the close of the eighteenth century, while 
Lamarck was meditating his Hydrog¢ologie, and had 
begun to study the invertebrate fossils of the Paris 
tertiary basin. 
His object, he says in his work, is to present cer- 
tain 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 in- 
fluence and the movements of the waters on the sur- 
face of the globe? 
