HISTORY OF GEOLOGY 3 



When once the fact was established that the solid globe was 

 subject to change, men looked first to the more obvious and 

 violent natural forces as the agents of this change. To the occa- 

 sional destructive fury of the hurricane, the earthquake, and the 

 volcano was attributed far greater importance than to the ceaseless 

 but inconspicuous work of the rain and the river. Another reason 

 why sudden and violent catastrophes were regarded as the only 

 important factors of change, was the very general belief that the 

 earth was only a few thousand years old. If all the modifications 

 which the earth's surface has demonstrably undergone were effected 

 within such a comparatively brief period, then they must have 

 been accomplished suddenly and violently and, in great part, by 

 agencies of which we have had no experience. Thus, all sorts of 

 fantastic causes, such as collisions with comets' tails, were conjured 

 up to account for the facts, and speculation ran riot. 



The purely arbitrary character of these speculations and fancies 

 rendered them unsatisfactory to thinking men. The progress of 

 astronomy had gradually familiarized their minds with the idea of 

 the almost infinite distances which separate the heavenly bodies, 

 and with the conceptions of order and the uniform operation of 

 law. These conceptions made the supposed cataclysms and con- 

 vulsions of the earth's history seem unnatural and improbable,, and 

 led geologists to inquire whether simpler explanations could not 

 be devised. This, in turn, led to the careful study of those modi- 

 fications of the earth's surface which are still in progress. Gradu- 

 ally the conviction grew, that the agencies which are still at work 

 upon and within the globe are the same as those which brought 

 about the manifold changes of the past, and that the earth's his- 

 tory is one of vast and unimaginable length. Scholars made little 

 progress in deciphering the Egyptian hieroglyphics until the dis- 

 covery of the Rosetta Stone, with its bilingual inscriptions, fur- 

 nished the key. So the geologists found that one key to the past 

 was to be found in the study of the forces which may be observed 

 in actual operation at the present time. 



Another advance was made while the disputes regarding the 

 nature of geological forces and the length of geological time were 



