52 Dr. T. Sterry Hunt — On Chemical Geology, 



chloric acid would result. Even if, as Mr. Forbes supposes, chlorid of sodium 

 were to be formed in the heated atmpsphere, it would be precipitated into a bath 

 of fused silicates, covered by an intensely heated atmosphere containing water, or 

 mingled oxygen and hydrogen gases, and would immediately undergo the same de- 

 composition that takes place when the vapors of common salt are diffused through 

 a potter's kiln, or, as in Mr. Gossage's new soda-process, are passed with steam 

 over red-hot flints. In both cases silicates of soda are formed with separation of 

 hydrochloric acid. 



These considerations lead to the conclusion that after all the more fixed elements 

 were precipitated, the whole of the chlorme would finally remain in the partially 

 cooled atmosphere as hydrochloric acid, and the whole of the sulphur as sulphurous 

 acid, together with a large proportion of oxygen, since we find this element in the 

 form of sulphate and not as sulphite in the sea-waters. Mr. Forbes does not, it 

 seems, believe that an excess of oxygen could exist in an atmosphere highly charged 

 with sulphurous acid ; and elsewhere (in the Chemical News), he tells that it is, 

 "if not impossible, at least highly improbable, that such a heated atmosphere con- 

 taining sulphurous acid, hydrochloric acid, with oxygen and aqueous vapor, could 

 exist," the elements being in his opinion incompatible. He is aware that at cer- 

 tain temperatures sulphurous acid and oxygen unite, in the presence of water, to 

 form oil of vitriol, but he forgets that at a higher temperature this compound is 

 again resolved into water, sulphurous acid and oxygen ; and that one of the best 

 processes for preparing the latter gas on a large scale is by this decomposition of 

 sulphuric acid, and the subsequent removal of the sulphurous acid from the cooled 

 gaseous mixture. Tn the opinion of Mr. Forbes, as set forth in the Chemical News, 

 the sulphurous and hydrochloric acids would decompose each other in the presence 

 of watery vapour (though every chemist's experience teaches him the contrary) ; 

 another reason for holding that my supposed atmosphere was impossible. Un- 

 fortunately for his opinion, however, it happens that large quantities of precisely 

 such an atmosphere are disengaged from various volcanic vents. To cite one 

 among many examples examined by Charles Deville and Leblanc (Ann. de Ch. et 

 Phys [3] lii. pp. 5-63), a /?/w^r<?//^ of Vesuvius yielded in June, 1856, a mixture of 

 highly heated steam, hydrochloric acid, sulphurous acid and air containing 18.7 

 per cent, of oxygen. The sulphurous acid was equal to 2.6 per cent, of the air, 

 and the amount of hydrochloric acid was about five times as great. Traces of 

 sulphuric acid were found in the water condensed from this steam, doubtless 

 formed by the slow combination of the sulphurous acid and oxygen ; and I may 

 state for the information of Mr. Forbes, that it was doubtless by a similar reaction 

 that the sulphurous acid became eliminated from the primeval atmosphere. We 

 have here, I may remark, an illustration of the fact upon which I have elsewhere 

 insisted, that volcanoes reproduce, on a limited scale, the conditions of the primeval 

 earth, not only in their solid but in their gaseous products. 



Mr. Forbes next asserts that, according to my view, "the hydrochloric acid 

 primeval atmosphere was derived from the mutual re-actions of sea-salt, silica, and 

 in the water" (page 438), and then charges me with the folly of "supposing the 

 pre-existence of compound bodies in a case where he had previously informed us 

 that there were only dissociated elements engaged." Mr. Forbes knows better 

 than this, or at least did know better when he wrote his criticism on my lecture in 

 the Chemical News of Oct. 4, for he here quotes my own words, when, in describ- 

 ing the cooling globe, the conditions through which it must have passed, and the 

 affinities brought into play, I say the products must have been '•^ just what would 

 now result if the solid land, sea, and air 7vere made to react upon each other tender 

 the influence of intense heat.'''' It is so difiicult to characterise properly such a wilful 

 perversion of an author's words that I must leave the task to my readers. What 

 follows in Mr. Forbes's paper as to chlorids, etc., I have already discussed and 

 disposed of. The theoiy of the constitution of the solid globe next put forward by 

 Mr. Forbes, borrowed from Phillips, Durocher, and Von Waltershausen, is also, as 

 I conceive, met by the argument in the previous pages. When, however, he comes 

 to the atmosphere surrounding his primitive globe, Mr. Forbes puts forward a 

 scheme which is strikingly original. He supposes around the "solidified crust," a 

 dense vapour consisting chiefly of chlorid of sodium, "above this a stratum of 

 carbonic acid gas, and then of water in the form of steam, whilst the oxygen and 

 nitrogen would be elevated still higher" (p. 439), probably, also, separated in the 



