STRABO. 21$ 



mained the same, but that it has been and is the 

 land which has been or is upheaved or subsided. It 

 is a fundamental truth on which much of the science 

 of geology depends. He moreover asserted that 

 volcanoes were safety-valves, and were the result 

 of subterranean convulsions. 



These were the principal writers which in- 

 fluenced geology in the days before the Christian 

 era, and it is to be noticed that they did not treat 

 of the construction of the rocks, of the succession of 

 the layers or strata, or of much concerning the 

 ancient history of the globe. But they taught, 

 wisely and admirably, the nature of modern 

 changes, and believed that these and the older ones 

 they could comprehend, were part of a scheme, and 

 were produced by natural causes, in the course of 

 events. 



Aristoteles, Strabo, and Plinius wrote about the 

 changes which were progressing on the surface of 

 the earth, and compared them, in their reasoning, 

 with changes they presumed had been, but still no 

 great advance was made. 



In the early part of the sixteenth century a 

 remarkable discussion sprang up about the nature 

 of shells and bones, which were found in layers of 

 earth remote from the sea. The celebrated painter 

 Leonardo da Vinci had seen some of these fossils 

 during his youth, when he planned and carried out 

 some important canals in the north of Italy. He 

 laughed at the fancies of the day about the shells, 

 for some people said that they were made by the 



