9i CHRONOLOGICAL ARRANGEMENT (Ch. VIII. 



living beings. During this state of things some of the residuary mineral 

 ingredients of the primaeval ocean were precipitated, and formed deposits 

 (the transition strata of Werner), half chemical and half mechanical, and 

 containing a few fossils. 



By this new theoiy, which was in part a revival of the doctrine of 

 Leibnitz, published in 1680, on the igneous origin of the planet, the old 

 ideas respecting the priority of all crystalline rocks to the creation of or- 

 ganic beings, were still preserved ; and the mistaken notion that all the 

 semi-crystalline and partially fossiliferous rc/cks belonged to one period, 

 while all the earthy and uncrystalline formations originated at a subse- 

 quent epoch, was also perpetuated. 



It may or may not be true, as the great Leibnitz imagined, that the 

 whole planet was once in a state of liquefaction by heat ; but there are cer- 

 tainly no geological proofs that the granite which constitutes the founda- 

 tion of so much of the earth's crust was ever at once in a state of universal 

 fusion. On the contrary, all our evidence tends to show that the formation 

 of granite, like the deposition of the stratified rocks, has been successive, 

 and that different portions of granite have been in a melted state at dis- 

 tinct and often distant periods. One mass was solid, and had been frac- 

 tured, before another body of granitic matter was injected into it, or through 

 it, in the form of veins. Some granites are more ancient than any known 

 fossiliferous rocks ; others are of secondary ; and some, such as that of 

 Mont Blanc and part of the central axis of the Alps, of tertiary origin. 

 In short, the universal fluidity of the crystalline foundations of the earth's 

 crust, can only be understood in the same sense as the universality of the 

 ancient ocean. All the land has been under water, but not all at one 

 time ; so all the subterranean unstratified rocks to which man can obtain 

 access have been melted, but not simultaneously. 



In the present work the four great classes of rocks, the aqueous, plutonic, 

 volcanic, and metamorphic, will form four parallel, or nearly parallel, col- 

 umns in one chronological table. Tbey will be considered as four sets of 

 monuments relating to four contemporaneous, or nearly contemporaneous, 

 series of events. I shall endeavor, in a subsequent chapter on the plutonic 

 rocks, to explain the manner in which certain masses belonging to each 

 of the four classes of rocks may have originated simultaneously at every 

 geological period, and how the earth's crust may have been continually 

 modelled, above and below, by aqueous and igneous causes, from times 

 indefinitely remote. In the same manner as aqueous and fossiliferous 

 strata are now formed in certain seas or lakes, while in other places vol- 

 canic rocks break out at the surface, and are connected with reservoirs of 

 melted matter at vast depths in the bowels of the earth, — so, at every 

 era of the past, fossiliferous deposits and superficial igneous rocks were in 

 progress contemporaneously with others of subterranean and plutonic ori- 

 gin, and some sedimentary strata were exposed to heat and made to as- 

 sume a crystalline or metamorphic structure. 



It can by no means be taken for granted, that during all these changes 

 the solid crust of the earth has been increasing in thickness. It has been 



