68 The Founders of Geology LECT. 



the elements. The facts known to him suggested an 

 arrangement of them into three groups or epochs, which 

 were not meant to imply definite periods of time or pre- 

 cise dates, but would express the idea of a recognizable 

 succession of events. His researches had assured him 

 that the volcanic history of Auvergne " formed a whole, 

 which, though incomplete, showed that Nature had fol- 

 lowed the same order of procedure in the most remote 

 ages as in the most recent times." 



In co-ordinating the appearances presented by the 

 different volcanic masses, he began with the consideration 

 of what were obviously the youngest, on the principle that 

 the last operations of Nature are simpler, and have under- 

 gone less modification from the influences which are con- 

 tinually changing the face of the land. He perceived that 

 volcanoes are only temporary accidents in the midst of the 

 ordinary and normal operations of nature, that the materials 

 erupted by volcanoes, at various intervals from a remote 

 antiquity, must have suffered from the universal degradation, 

 and that the extent of their waste would be proportionate 

 to the length of time during which the loss had been 

 continued. The latest lavas must unquestionably present 

 most nearly the primitive forms of volcanic masses, and 

 should thus serve as a standard for comparison, to be kept 

 before the eyes of every observer who would judge correctly 

 of the extent and progress of the alteration that is to be 

 seen in other regions. 



The first of his three periods includes the products of 

 still active and recently extinct volcanoes. These are 

 distinguished by the association of crater-bearing cones of 

 cinders and scoriae, with streams of rugged lava, which can 



