The Chemistry of the Primeval Earth. 365 



chemical process by which, the carbonic acid has been separated 

 from the air, the agency which has progressively purified our 

 atmosphere, and has fitted it for the support of the higher forms of 

 animal life, so that every clod of clay represents a very instructive 

 series of processes. That clod of clay tells us of the decomposition 

 of an old felspathic or granitic rock as it were — of the separation 

 from it of carbonate of soda, — of the decomposition of the salts of 

 lime in the sea water, — of the formation, therefore, of an equivalent 

 of carbonate of lime, — of the formation of common salt,— and of the 

 separation from the atmosphere of an equivalent of carbonic acid ; 

 and thus the great law of equilibrium binds together the composi- 

 tion of the solid crust of the earth, of the waters, and of the air. 



We have thus considered two great sets of action. Principally, 

 however, I should say we have considered the action from without — 

 the action of acids and gases and vapors upon the solid crust of the 

 earth. But you will ask, is there no action from within ? Geolo- 

 gists have been prone to assign the action of the central fire as the 

 source of almost all the changes which take place at the surface of 

 the earth ; and shall we exclude that from our scheme ? No, cer- 

 tainly not ; but I dare say that when I spoke of this solid crust of 

 the earth, the question was asked by many in their own minds 

 whether that first-formed crust was not identical with granite. It 

 is a very common notion that granite forms the substratum of the 

 earth — that it was the rock upon which all other rocks were built. 



Now, in the first place, I would remark that we have not evidence 

 anywhere of an exposed portion of that crust of the earth. In fact, 

 by the very conditions of the problem, as I have put them forward, 

 we would conceive a complete decomposition, a complete destruction, 

 of all that crust either by submarine or subaerial agency, — the break- 

 ing of it down into clay or into other elements of that kind, so that 

 everywhere the primitive crust of the earth is buried beneath its own 

 ruins. But if we may be permitted to imagine the composition of 

 that primitive crust — to reconstruct it, so to speak, as I have just 

 now done — you will see that its composition would have excluded 

 altogether free silica, — would have excluded quartz, and that this 

 very quartz, which is one of the constituent elements of granite, is 

 only the result of a secondary chemical process which I have just 

 explained to you ; so that, in fact, the granites and the gniesses and 

 all these rocks which at the earth's surface now appear in a disruptive 

 extruded form are, in fact, older rocks decomposed by water — the 

 results of the metamorphism of the older rocks themselves deposited 

 from water. 



One point (and I beg pardon for having omitted it just now) with 

 regard to the composition of this earlier atmosphere. Unfitted as 

 it was for the higher forms of life, still from the comparatively large 

 amount of carbonic acid present, it would seem to have been pecu- 

 liarly fitted for the development of luxuriant vegetation ; and it was 

 long since pointed out by Brongniart that we might suj)pose a mar- 

 vellous luxuriance of vegetation in earlier periods of the earth which 

 gave rise to enormous beds of coal and other fossil fuel ; for we 



