The Chemistry of the Primeval Earth. 367 



carbonic acid : the whole phenomena of limestone require it ; and, in 

 fact, the whole chemical conditions for this hypothesis which I am 

 explaining to you require it. Let us see what will be the effect of 

 preparing an artificial atmosphere. If we endeavour to reconstitute 

 such an atmosphere as must have involved this globe at the time 

 these rocks were being deposited, let us see whether we cannot get 

 the conditions for the formation of these rocks. In an apparatus 

 fitted for the purpose I surrounded the required materials with such 

 an atmosphere as existed in the coal-period, and I found that under 

 that artificial atmosphere, providing the conditions for evaporation, 

 the whole series of phenomena went on perfectly, and there was no 

 difficulty in producing carbonate of magnesia and gypsum ; and, in 

 fact, I had here another confirmation of the notion of the highly 

 carbonated condition of the atmosphere in palssozoic and mesozoic 

 times. That theory is confirmed by climate, by vegetation, and by 

 the singular series of reactions w hich have hitherto been a perplexity 

 to chemical geologists. 



But we have hitherto been considering, as I said before, only super- 

 ficial actions — actions in which gases and vapors and matters diffused 

 in the atmosphere are operating to produce the slow decay, crumbling 

 down, denudation, and disintegration of the solid crust so that the first 

 inequalities of the earth's surface would be rapidly effaced ; and the re- 

 sult of all this would be, to reduce the whole surface of the earth to a 

 dead level were it not that there is below a counteracting force, and 

 that that counteracting force is no other than the central heat, that 

 central heat operating directly upon these buried sediments, giving to 

 the lower strata a softness and plasticity so that they give way under 

 the superincumbent pressure of accumulated masses of sand, and of 

 clay and of gravel. These slowly send the other matters down until 

 they came within the sphere of the central heat, and thus they in- 

 directly produce those effects which have been by most writers attri- 

 buted to direct outbursts of the central fire. The generally received 

 opinion is, as you are aware, that volcanoes and igneous eruptions 

 have their seat in this great fluid bath, upon which floats the thin 

 crust upon which we live ; but in the great density of these solidify- 

 ing cooling rocks I have already demonstrated a chemical reason for 

 repudiating that doctrine. 



It would be foreign to my object to-night to enter into a dis- 

 cussion of the physical, mathematical, and astronomical reasons, 

 which have been given against that doctrine, and which go power- 

 fully to support this practical reasoning. I may ajDpeal, however, 

 to the labours of the late Mr. Hopkins, of Cambridge, who, by his 

 admirable combination of mathematical and geological science, con- 

 tributed so much to the advancement of geology. He was able, by 

 very careful calculation upon the precession of the equinoxes and 

 upon the phenomena of mutation, to conclude that the earth, if not 

 solid to the core, must be almost solid ; and Professor Thompson, 

 from the theory of the tides, and Archdeacon Pratt, of Calcutta, have 

 also arrived at conclusions which support completely those arrived 

 at from purely chemical data, namely, the essential solidity of the 



