GEOLOGY. 



GEOLOGY or Geognosy, for the terms are nearly synonymous, 

 is that branch of science which treats of the terrestrial globe, 

 considered principally with regard to the nature and disposition 

 of the mineral masses of which the crust of the earth is com- 

 posed. This branch of science had scarcely an existence, till 

 Saussure and Werner pointed out the bases upon which it was 

 founded. The first of these philosophers, by a laborious inves- 

 tigation of the most inaccessible mountain districts, during twen- 

 ty years of continual research, demonstrated the order of the 

 primitive formations, and traced the boundaries which distin- 

 guish them from such as are later in point of time ; and Wer- 

 ner, taking advantage of the numerous excavations in some of 

 the oldest mining districts, first classified the rocks of which 

 the crust of the earth is composed, attempted to fix the laws 

 which appear to regulate the succession of strata, pointed out 

 their relative antiquity, and traced their various changes. To 

 these names may be added that of Baron Cuvier, whose dis- 

 coveries in the natural history of fossil organic remains and 

 their distribution, have given new interest to geological inves- 

 tigations. Numerous other writers have at various periods 

 contributed to extend the science of geology, either by the 

 communication of facts or the proposal of theories to explain ex- 

 isting appearances. Among these it is only necessary to men- 

 tion Whitehurst, Hutton and Playfair, Greenough, Buckland, 

 and Jameson. And societies for the special purpose of geological 

 investigation have been formed in various parts of the world. 



In a general view, the surface of the globe is composed of 

 land and water. The water occupies nearly three-fourths of the 

 surface, and the land above its level is arranged into masses 

 varying in magnitude and form. This land, however, is not 

 equally distributed ; for a much larger portion occurs to the 

 north than to the south of the equator ; and while the southern 

 half is occupied chiefly by water, the northern division is prin- 

 cipally land. 



