Biographical Memoir of H&ivry Cavendish, 223 



has been, according as the researches have been directed toward 

 the forms of the organic world, or toward the inanimate mass 

 of the earth. Different forms of plants and animals enliven the 

 earth's surface in each zone, however much the heat of the at- 

 mosphere may change, whether according to the geographical 

 latitude, or the numerous curves of the isothermal lines, in the 

 extended plains, level as the surface of the sea, or in an almost 

 vertical direction on the steep slopes of the mountain chains. 

 Organic nature gives to each region of the earth the peculiar 

 physiognomy by which it is distinguished. The case is different 

 with inorganic nature in the places where the solid envelope of 

 the earth is deprived of vegetation. The same species of rocks, 

 attracting and repelling each other by groups, disclose them- 

 selves in the two hemispheres, from the equator to the poles. 

 In a distant isle, surrounded by unknown plants, in a clime 

 where the stars to which his eye is habituated no longer shine, 

 the voyager often recognises with joy the granite of his native 

 country, and the rocks which he has been accustomed to see. 



This independence upon the present constitution of climates, 

 which is peculiar to inorganic nature, does not diminish the be- 

 neficial influence which numerous observations, made in distant 

 countries, have upon the progress of geognosy ; it only gives 

 them a particular direction. Each succeeding expedition en- 

 riches natural Jiistory with new species of animals and plants. 

 Sometimes organic forms are discovered which connect them- 

 selves with types long known, and which present in its original 

 perfection the regularly woven, and often apparently interrupt- 

 ed, net-work of animated natural forms. Sometimes the dis- 

 coveries consist of forms which present themselves isolated, like 

 the remains of extinct races ; sometimes of members of yet un- 

 known groups. The examination of the solid crust of the earth 

 exhibits no such diversity. On the contrary, it discloses, in the 

 constituent parts, in the relative position, and in the periodical 

 recurrence of the different masses, a similarity which strikes the 

 geologist with astonishment. In the chain of the Andes, as in 

 the central mountains of Europe, one formation seems, as it 

 were, to recal another. Masses of the same name assume simi- 

 lar forms; the basalt and greenstone form twin mountains; 

 dolomite, white sandstone and porphyry, form masses broken 



