28 NECESSITY OP GENERAL 



heat throws a faint light on the early history of our planet, 

 by showing the possibility of a generally prevalent tropical 

 climate, arising from the heat issuing from crevices in the 

 recently oxydized crust of the globe ; a state of tilings in 

 which the temperature of the atmosphere would depend far 

 more on the reaction of the interior of the planet upon its 

 crust, than on its relative position in respect to the central 

 body or sun. 



The cold zones of the earth present to the researches of 

 the geologist many buried products of a tropical climate : 

 in the coal formations, upright stems of palms, coniferse, 

 and tree ferns, goniatites, and fishes with rhornboidal ena- 

 melled scales ( 41 ) ; in the Jura limestone, colossal skeletons of 

 crocodiles and long-necked Plesiosauri, Planulites, and stems 

 of Cycadese; in the chalk, small Poly thalainia and Bryozoa, 

 in part identical with some of our living marine animals; in 

 tripoli or polishing slate, in semi-opal, and in the substance 

 called mountain meal, agglomerated masses of fossil infu- 

 soria, such as Ehrenberg's all-animating microscope has 

 disclosed to us ; and lastly, in transported soils and in caves, 

 bones of hyenas, lions, and elephantine Pachydermata. An 

 enlarged knowledge of other natural phsenomena renders 

 these objects no longer an occasion for mere barren curiosity 

 and wonder, but for intelligent study and profound medita- 

 tion. 



The multiplicity of diverse objects^ which I have here 

 purposely crowded together, leads directly to the question, 

 whether general views of nature can possess a sufficient 

 degree of clearness, without a deep and earnest application 

 to separate studies, whether of descriptive natural history, of 

 geology, of physics, or of mathematical astroromy ?' In 



