INTRODUCTION. 43 



To the second epoch (circa 35,000 years) Buffon assigns the 

 gradual consolidation of the material at the earth's surface. 

 The occurrence of rents in this primitive crust allowed the 

 influx of molten metallic ores, and was the first cause of surface 

 irregularities. At the commencement of the third epoch (ca. 

 15-20,000 years), the cooling of the earth proceeded so far that 

 the atmospheric vapours were precipitated and gave origin to 

 the primitive universal ocean. Then began the development of 

 life in the warm waters and the accumulation of marine sedi- 

 ments. Gradually the mountains and continents appeared, the 

 tapering of the continents towards the south being due to the 

 rush of oceanic currents from south to north. The fourth 

 period (ca. 5000 years) was signalised by a sudden accession 

 of the earth's internal heat, with the result that violent volcanic 

 eruptions burst forth, and were accompanied by gigantic 

 convulsions of the earth's crust. 



The fifth period saw calm restored, but the equatorial regions 

 were still so hot as to be uninhabitable. Life flourished over 

 large continental regions at the Poles, and the large terrestrial 

 animals, elephants, mastodons, the rhinoceros, and others, came 

 into existence. As the heat continued to diminish, the faunas 

 and floras gradually migrated southward. 



The sixth period saw the decimation of a continuous 

 northern continent into several portions, and many local 

 changes in the extent and position of the seas. Man appeared 

 and began to struggle with lower creation for the means of 

 existence. 



The seventh period is the epoch of Man's lordship in the 

 world, and this will continue until the earth cools to a tempera- 

 ture twenty-five times colder than that of the present age, when 

 all Creation on the Earth's surface will be annihilated. 



Buffon's merit consists in the bold construction and masterly 

 exposition of a theory which for the first time brought the 

 historical possibilities of geology to the forefront. His calcu- 

 lation of the duration of the successive epochs had, it is true, 

 no empirical basis. Yet it made sufficiently clear to all readers 

 the author's desire to insist upon long periods of time for the 

 slow processes of change in the earth's configuration, and for 

 the appearance of successive forms of plant and animal life. 

 Some of the noteworthy advances made by Buffon were the 

 differentiation which he drew between the primitive rocks 

 formed in the second period, and the sedimentary and volcanic 



