NATURAL SCIENCE IN THE NINETEENTH CENTURY 385 



Hutton and Smith, eventually overthrew catastrophism and 

 established uniformitarianisin in its place. (See Appendix H.) 



GLACIERS AND GLACIAL THEORIES. The occurrence on the 

 earth's surface, and even on mountain tops, of boulders evidently 

 of distant rather than local origin, had long been a puzzle even to 

 geologists. The primitive hypothesis of their deposit during the 

 Flood the so-called diluvial theory no longer sufficed to 

 satisfy inquiring minds, and equally inadequate was the idea of 

 von Buch that boulders had been thrown up like cannon shot by 

 volcanoes and had fallen where found. In 1837 Louis Agassiz 

 (1807-1873) advanced the present doctrine : viz. that boulders 

 have been deposited after the melting of masses of ice by which 

 they were slowly brought from a distance. Agassiz supported 

 this ice or "glacial" theory by personal observations and studies 

 of the glaciers of the Alps, and eventually propounded that gen- 

 eral theory of glaciation or ice caps at the earth's poles which is 

 now universally accepted. Few theories have ever proved more 

 satisfactory, scientifically speaking, more popular, in the best 

 sense, or more productive of simple explanations of widespread 

 and diverse phenomena. We have only to set over against the 

 glacial the diluvial theory, with its fatal weakness in requiring the 

 transportation by water of huge masses of rock over long distances, 

 or the projectile theory, with its requirement of showers of flying 

 boulders falling almost anywhere, to realize the simplicity and 

 adequacy of the glacial theory. The word " boulder," nevertheless, 

 remains as a reminder of the diluvial theory, since it is derived 

 from words signifying "the noise of a stone in a stream." 



RISE OF PALEONTOLOGY. Before the nineteenth century 

 precise knowledge of extinct animals and plants was almost wholly 

 wanting. Fossils had indeed been observed from the earliest 

 times but although occasionally correctly interpreted, as for ex- 

 ample by Pythagoras and Xenophanes, Leonardo da Vinci and 

 Palissy. Hooke (p. 268) at the end of the seventeenth century first 

 made the important suggestion that fossils might serve as indicators 

 of phases in the earth's history and as proof of the existence at one 

 time of a tropical climate in England. In the eighteenth century 

 2o 



