350 FOSSILS 



bottom. Unconformities, more or less wide-spread, offer a natural 

 and convenient mode of dividing the strata into groups, but the 

 difficulty with this method is that the dates of elevation and de- 

 pression so seldom correspond in different regions, that divisions 

 thus made are apt to be of more or less local validity. The only 

 standard yet devised which is applicable to all the world is that 

 founded upon the progress of life. 



The comparison between human history and geological history 

 is one that has very often been made, but trite and hackneyed as 

 it is, it is none the less instructive. The history of civilized na- 

 tions is the record of continuous development, not without retro- 

 gressions and periods of comparative stagnation, but having no 

 actual gaps in it. For the sake of convenience, history is divided 

 into certain periods in accordance with the predominance of cer- 

 tain great ideas and principles, and these periods are real, repre- 

 senting the salient facts in the progress of development. Each 

 period is, however, but the outcome of the antecedent periods, 

 and the ideas and principles which characterize it were slowly 

 maturing, it may be through centuries, and even after other ideas 

 have risen to predominance, older ones continue to live and influ- 

 ence the world. For example, when we speak of the age of the 

 French Revolution, we refer to a time when a certain set of politi- 

 cal ideas and principles were the most striking and influential 

 factors in the development of the civilized world, beginning with 

 the visible changes of 1789 and ending with the restoration of the 

 Bourbons in 1815. But the tremendous outbreak was slowly pre- 

 paring throughout the Eighteenth Century ; the conflagration was 

 proportionate to the materials that had been gathered for it. Nor, 

 on the other hand, could the effects of the great movement be 

 undone by the return of the exiled king. To this day the whole 

 civilized world feels the effects of the convulsion, and the entire 

 course of the Nineteenth Century would have been different but 

 for the French Revolution. 



Historians are careful to distinguish between events and the 

 record of them. Events are continuous and bound up into a 

 chain of consequences, every one of which is dependent upon 



