62 COSMOS. 



the descriptive natural history of all organized beings, are the 

 fruitful sources whence we draw the materials necessary to 

 give a solid basis to the study of the mutual relations and 

 connection of phenomena. 



We will here subjoin one important observation by way of 

 elucidating the connection of which we have spoken. The 

 first general glance over the vegetation of a vast extent of a 

 continent shows us forms the most dissimilar — Graminese and 

 Orchideee, Coniferse and oaks, in local approximation to one 

 another ; while natural families and genera, instead of being 

 locally associated, are dispersed as if by chance. This disper- 

 sion is, however, only apparent. The physical description of 

 the globe teaches us that vegetation every where presents nu- 

 merically constant relations in the development of its forms 

 and types ; that in the same climates, the species which are 

 wanting in one country are replaced in a neighboring one by 

 other species of the same family ; and that this laiv of substi- 

 tution, which seems to depend upon some inherent mysteries 

 of the organism, considered with reference to its origin, main- 

 tains in contiguous regions a numerical relation between the 

 species of various great families and the general mass of the 

 phanerogamic plants constituting the two floras. We thus 

 find a principle of unity and a primitive plan of distribution 

 revealed in the multiplicity of the distinct organizations by 

 which these regions are occupied ; and we also discover in 

 each zone, and diversified according to the families of plants, 

 a slow but continuous action on the aerial ocean, depending 

 upon the influence of light — the primary condition of all or- 

 ganic vitality — on the solid and liquid surface of our planet. 

 It might be said, in accordance with a beautiful expression of 

 Lavoisier, that the ancient marvel of the myth of Prometheus 

 was incessantly renewed before our eyes. 



If we extend the course which we have proposed, following 

 in the exposition of the physical description of the earth to the 

 sidereal part of the science of the Cosmos, the delineation of 

 the regions of space and the bodies by which they are occupied, 

 we shall find our task simplified in no common degree. If, ac- 

 cording to ancient but unphilosophical forms of nomenclature, 

 we would distinguish between physics, that is to say, general 

 considerations on the essence of matter, and the forces by which 

 it is actuated, and chemistry, which treats of the nature of 

 substances, their elementary composition, and those attrac- 

 tions that are not determined solely by the relations of mass, 

 we must admit that the description of the earth comprises at 



