1896.] Principles of Geology, and i 



183 



of forming rocks and of bringing about the changes that have 

 occurred on the earth. He held that the strata which now 

 compose the continents were once beneath the sea, and were 

 formed out of the waste of preexisting continents by the action 

 of the same forces which are now destroying even the hardest 

 rocks. Hutton was the kind of man the science had so long 

 been in need of, and by his teaching geologists were at last 

 started on the only path that could possibly lead them to 

 truth. He drove out at once and forever the imaginary agen- 

 cies which the early geologists had been so ready to have re- 

 course to, and laid down the principle that in geological spec- 

 ulation " no powers are to be employed that are not natural 

 to the globe, no actions to be admitted of except those of which 

 we know the principle, and no extraordinary events to be al- 

 leged in order to explain a common appearance." He occu- 

 pied himself mainly studying the changes that are now taking 

 place on the earth's surface, and the means by which they 

 were brought about, and in demonstrating the fact that the 

 changes that had happened during the past periods of the 

 earth's history were of the same kind and due to the same 

 causes as those now going on. 



The determination of the order 6f the strata, and the group- 

 ing of them in chronological order, were begun by Lehman 

 (1756) and carried on by Fuchsel (1773), Pallas (1785) and 

 Werner (1789). Smith made the most important contribution 

 to this subject when, in 1790, he published his Tabular View 

 of the British Strata. He showed their superposition and char- 

 acterized the different groups by their peculiar fossils. 

 (To be continued.) 



