18G7.] HUNT — THE CHEMISTRY OF THE EARTH. 220 



presented probably au irregular, diversified surface from the result 

 of contraction of the congealing mass, which at last formed a liquid 

 bath of no great depth, surrounding the solid nucleus. It is to the 

 composition of this crust that we must direct our attention, since 

 therein would be found all the elements (with the exception of 

 such as were still in the gaseous form) now met within the known 

 rocks of the earth. This crust is now everywhere buried beneath 

 its own ruins, and we can only from chemical considerations 

 attempt to reconstruct it. If we consider the conditions through 

 which it has passed, and the chemical affinities which must have 

 come into play, we shall see that there are just what would now 

 result if the solid land, sea, and air were made to react upon each 

 other under the influence of intense heat. To the chemist it is at 

 once evident that from this would result the conversion of all 

 carbonates, chlorides and sulphates into silicates, and the separa- 

 tion of the carbon, chlorine, and sulphur in the form of acid gases, 

 which, with nitrogen, watery vapour, and a probable excess of 

 oxygen, would form the dense primeval atmosphere. The resulting 

 fused mass would contain all the bases as silicates, and must have 

 much resembled in composition certain furnace-slags or volcanic 

 glasses. The atmosphere, charged with acid gases which sur- 

 rounded this primitive rock must have been of immense density. 

 Under the pressure of such a high barometric column, condensa- 

 tion would take place at a temperature much above the present 

 boiling point of water, and the depressed portions of the half- 

 cooled crust would be flooded with a highly heated solution of 

 hydrochloric acid, whose action in decomposing the silicates is 

 easily intelligible to the chemist. The formation of chlorides of 

 the various basis, and the separation of silica, would go on until 

 the affinities of the acid were satisfied, and there would be a separa- 

 tion of silica, taking the form of quartz, and the production of 

 a sea-water holding in solution,^ besides the chlorides of sodium, 

 calcium, and magnesium, salts of aluminium and other metallic 

 basis. The atmosphere, being thus deprived of its volatile chlorine 

 and sulphur compounds, would approximate to that of our own 

 time, but differ in its greater amount of carbonic acid. 



We next enter into the second phase in the action of the atmos- 

 phere upon the earth's crust. This, unlike the first, which was 

 subaqueous, or operative only on the portion covered with the 

 precipitated water, is sub-aerial, and consists in the decomposition 

 of the exposed parts of the primitive crust under the influence of 



