THE DOGMA OF EVOLUTION 



telian he points out that the element, fire, is as im- 

 portant a constituent of the world as is water. The 

 tendency of fire is to rise and, in its effort to seek its 

 natural place, it raises the earth's crust with it, as is 

 proved by volcanic action. These two opposing forces, 

 the gravitation of water and the levitation of fire can 

 evidently account for a cyclic action of the earth's 

 surface, now tending to smooth it and now to make 

 it unequal, according as the one or the other force is 

 predominant. For the refutation of the second point, 

 he admits the evidence of the emergence of some 

 places, but he adds that other places show an equal 

 subsidence since, for example, the Island of Sicily 

 was once, undoubtedly, joined to the main-land of 

 Italy. Thus, the second point fails to prove the finite 

 duration of the world since the sea may not be sink- 

 ing, but the land alternately rising and falling. Theo- 

 phrastus had grasped clearly the scientific and basic 

 principle of geology; that the changes in the earth's 

 surface are caused by two opposing forces, aqueous 

 erosion and igneous eruption. But, on the other hand, 

 he entirely fails to inquire whether the fossils were 

 the remains of marine animals which had become ex- 

 tinct. 



The correct geological ideas of Theophrastus were 

 carried down through the Middle Ages by the Arabic 

 philosophers as we know from several references. The 

 most important evidence is probably that of Albertus 

 Magnus who refers to a treatise On Minerals by Avi- 



n 126 3 



