GEOLOGY. 395 



fusible, includes amber, retinasphaltum, and bitumen: and the second 

 order, Jlnthracinea, or coal-like minerals, infusible, but combustible, 

 includes bituminous coal, which burns with a flame ; anthracite, 

 which burns without flame ; and graphite, which is a compound of 

 carbon with a small portion of iron, improperly called black lead. 

 We are constrained to express the opinion, that a still more natural 

 classification of minerals might be formed ; and that the distinctions 

 of being soluble, or earthy, or metallic, or inflammable, would be 

 proper types for four classes in which all minerals might naturally 

 be arranged. 



CHAPTER IV. 



GEOLOGY. 



GEOLOGY is that branch of Idiophysics, or Natural History, which 

 treats of the structure of the earth, and the masses which compose 

 it; and of the changes, both organic and inorganic, which it has 

 hitherto undergone, or to which it is still exposed. The name is de- 

 rived from the Greek, 777, the earth ; and ;*.oyo$, a discourse : and this 

 branch has also been termed Geognosy, from another Greek word 

 signifying knowledge, or science. As it is impossible to understand 

 the structure of mountain masses and rocks, without knowing the 

 simple minerals which compose them, the study of Geology evi- 

 dently presupposes and depends upon a knowledge of mineralogy. 

 As it includes the study of organic remains, or fossil plants and 

 animals, the study of which has received the name of Paleontology, 

 its connection with the other natural sciences will be distinctly per- 

 ceived ; and the more so, the farther we advance in its attainment. 

 While its practical importance, in the arts of Agriculture, Mining, 

 and Engineering, is generally recognized, it ranks with Archaeology 

 in its recondite researches, and with Astronomy in the sublimity of 

 its themes and results, as one of the most profound and interesting 

 of the sciences. 



Among the ancient philosophers, Thales believed that the earth 

 was of aqueous origin; an idea probably derived from the Egyptian 

 priests : while Zeno maintained that it was produced by the action 

 of fire. In modern times, Agricola of Saxony, and Bernard de 

 Palissy in France, were among the first to promulgate rational views 

 of the formation of minerals. Leonardo da Vinci, about A. D. 1500, 

 observing the shells of the Appenines, boldly maintained that those 

 mountains were formerly covered by the sea; an opinion which 

 thenceforward found advocates, and elicited new researches. The 

 idea of geological maps, appears to have originated with Dr. Lister, 

 in 1683 ; and the first notice that rocks and earths occur in regular 

 strata is attributed to Mr. Woodward ; who founded a geological 

 museum, as early as 1695. The division of rocks into primary, and 

 secondary, was first made bv Lehman of Germany, in 1756, and 

 confirmed by Arduino, in 1759 : and a more minute classification 

 was introduced by Werner. The importance of the study of fossils, 



