NATURAL HISTORY OF THE EIGHTEENTH CENT. 409 



of time, raised mountains from the abyss, has down to the present day 

 continued to produce others, in order to restore from time to time the 

 losses of all such as sink down in different places or are rent asunder, 

 or in other ways suffer disintegration. If this be admitted, we can 

 easily understand why there should now be found upon many moun- 

 tains so great a number of Crustacea and other marine animals." 

 (Generelli, as quoted by Sir C. Lyell.) 



LEHMANN, a German mineralogist, writing in 1756, distinguished 

 three different classes of mountains : first, those formed at the creation 

 of the earth, and before animals had appeared (these contained no 

 fragments of other rocks, and of course no organic remains); second, 

 rocks resulting from the partial destruction of the former, and also 

 without organic remains ; third, those produced by local convulsions, 

 and in part by the Deluge of Noah. 



The great earthquake of Lisbon, which in 1755 caused the death of, 

 60,000 persons, strongly attracted men's minds to the subject of earth- 

 quakes. The Rev. JOHN MICHELL, Professor of Mineralogy at Cam- 

 bridge, in 1760 published in the "Philosophical Transactions" an 

 " Essay on the Causes and Phenomena of Earthquakes." These he 

 attributed to the sudden generation of steam produced by the contact 

 of water with intensely hot matter, which he supposes exists at certain 

 depths below the surface. The steam thus generated forces its way 

 between the strata of the earth, heaving up one tract of country after 

 another. If the internal fire lie far below the surface, the earthquake 

 will move with great velocity over a large extent of country ; but when 

 the fire is near the surface the earthquake will affect a smaller extent 

 of country, and will move with less velocity. Michell, in pointing out 

 the application of his theory, describes the general horizontality of the 

 strata in low countries, and their disturbed state in the vicinity of chains 

 of mountains. His views are remarkable as anticipating those at which 

 geologists in general arrived only at a later date. 



FUCHSEL, a German physician, writing in 1762 1773, describes 

 geologically a certain district of Germany, and he recognizes the rela- 

 tion of the fossils of the various strata to their ages. The separation 

 of the rocks of the globe into separate groups became quite general 

 towards the end of last century. In 1778 PALLAS (1741 1811), after 

 having examined the two great mountain chains of Siberia, announced 

 that the granite rocks were in the middle, the schistose on their sides, 

 and the limestone outside of these last. He conceived that in all 

 mountain chains composed of primary rocks the same law would hold. 

 Worthy of mention is the discovery by the same naturalist of the 

 entire bodies of an elephant and a rhinoceros of extinct species, pre- 

 served for ages by being frozen up in ice-banks. 



The results obtained by the observations of all the preceding geo- 

 logists were reduced to a methodical system by WERNER (1750 1817), 

 who was Professor of Mineralogy at Freyberg in Saxony, and his lee- 



