102 EXPEDITION OF THE " CHALLENGER " n; 



skeletons, is correct, then all these deposits alike 

 would be directly, or indirectly, the product of 

 living organisms. But just as a silicious deposit 

 may be metamorphosed into opal or quartzite, and 

 chalk into marble, so known metamorphic agencies 

 may me^amdrgtose clay into schist, clay-slate, slate, 

 gneiss^ or , even granite. And thus, by the agency 

 of; the lowest and simplest of organisms, our 

 imaginary globe might be covered with strata, of 

 all the chief kinds of rock of which the known 

 crust of the earth is composed, of indefinite thick- 

 ness and extent. 



The bearing of the conclusions which are now 

 either established, or highly probable, respecting 

 the origin of silicious, calcareous, and clayey rocks, 

 and their metamorphic derivatives, upon the 

 archaeology of the earth, the elucidation of which 

 is the ultimate object of the geologist, is of no 

 small importance. 



A hundred years ago the singular insight of 

 Linnaeus enabled him to say that " fossils are not 

 the children but the parents of rocks," l and the 



1 "Petrificata montium calcariorum non filii sed parentes 

 sunt, cum omnis calx oriatur abanimaKbus." Systema Natures, 

 Ed. xii., t. iii., p. 154. It must be recollected that Linnseus 

 included silex, as well as limestone, under the name of " calx," 

 and that he would probably have arranged Diatoms among 

 animals, as part of "chaos." Ehrenberg quotes another even 

 more pithy passage, which I have not been able to find in any 

 edition of the Systema accessible to me: "Sic lapides ab 

 animalibus, nee vice versa. Sic rupes saxei non primsevi, sed 

 temporis filiae." 



