ANNOTATIONS AND ADDITIONS. 283 



respect to the sun and of latitude. Would not the climate of Ger- 

 many be wonderfully altered, and that perhaps for centuries, if there 

 were opened a fissure a thousand fathoms in depth, reaching from the 

 shores of the Adriatic to the Baltic ? If, in the present condition 

 of our planet, the stable equilibrium of temperature, first calculated 

 by Fourier in his Theorie analytique de lachaleur, has been almost 

 completely restored by radiation from, the earth into space ; and if 

 the external atmosphere now only communicates with the molten 

 interior through the inconsiderable openings of a few volcanoes in 

 the earlier state of things numerous clefts and fissures, produced by 

 the frequently recurring corrugations of the rocky strata of the 

 globe, emitted streams of heated air which mingled with the atmo- 

 sphere and were entirely independent of latitude. Every planet 

 must thus in its earliest condition have for a time determined its 

 own temperature, which afterwards Ibecomes dependent on the posi- 

 tion relatively to the central body, the Sun. The surface of the 

 Moon also shows traces of this reaction of the interior upon the 

 crust. 



( 41 ) p. 234. " The mountain declivities of the southern part of 

 Mexico." 



The greenstone, in globular concretions of the mountain district 

 of Guanaxuato, is quite similar to that of the Franconian Fichtel- 

 Grebirge. Both form grotesquely shaped summits, which pierce 

 through and cover the transition argillaceous schists. In the same 

 manner, pearl stone, porphyritic schists, trachyte, and pitch-stone 

 porphyry, constitute rocks similar in form in the Mexican mountains 

 near Cinapecuaro and Moran, in Hungary, in Bohemia, and in 

 Northern Asia. 



( u ) p. 236. "The Dragon-tree of Orotava.'' 

 This colossal dragon-tree, Dracaena draco, stands in the garden of 

 Dr. Franqui in the small town of Orotava, the ancient Taoro, one 

 of the most delightful spots in the world. In June, 1799, when we 

 ascended the Peak of Teneriffe, we measured the circumference of 

 the tree, and found it nearly 48 English feet. Our measurement 

 was taken several feet above the root. Lower down, and nearer to the 



