96 Correspondence — Mr, David Forbes, 



The carbonic acid, also, being so infinitely more dense, and present in so over- 

 whelming a quantify, would further act as a powerful shield against the very 

 oxidising action which Dr. Hunt lays such stress upon. 



That the chlorine did not go into the atmosphere, as Dr. Hunt imagines (com- 

 bined with hydrogen as hydrochloric acid), I infer from the well-known far 

 greater affinity which it has for sodium than for hydrogen, and the volatility of the 

 sodium would be far more likely to bring it in contact with the chlorine than with 

 the silica. 



The idea that the action of the feeble excess of oxygen above alluded to, in con- 

 nection with silica and steam, would prevent the formation of chloride of sodium, 

 is not of much weight, since the chloride of sodium would be formed as a vapour 

 in the atmosphere, while the silica remained below in the earthy mass in a solid 

 form. 



But Dr. Hunt next writes : "Even if, as Mr. Forbes supposes, the chloride of 

 sodium were to be formed in the heated atmosphere, it would be precipitated into 

 the intensely heated bath," etc. Precipitated ! when it would be in the state of 

 vapour at this temperature. 



Metallurgists know how indifferent chloride of sodium is when fused with silicates, 

 and to this property is due the employment of what is termed a salt-cover in assays ; 

 however well the salt may be intermixed, once the mass is fused it rises and 

 swims on the top, and (if the heat be not too elevated or protracted as to vola- 

 tilise it entirely) presents, upon cooling, a well-defined crystalline crust of salt, 

 below which is found the unaltered silicate slag, and below this again the button 

 of metal, pure or more or less in combination with sulphur, arsenic, antimony, 

 etc., as the case may be; thus presenting, on the small scale, an illustration of 

 what I have supposed may have occurred in nature, m which case also the cover 

 or crust of salt would act as a shield against oxidation. 



In a potter's kiln, the vapour of salt under confinement merely glazes the sur- 

 face of the ware to a minute depth, which very glaze protects the silicates 

 from further action ; but both the potter's kiln and Gossage's soda-process are 

 worked under forced circumstances, not applicable in this argument ; and when Dr. 

 Hunt explains that in his illustration of this subject he merely used the words, 

 '"'■ if the elements were made to react upon one aitotker,^^ is it not rather he who 

 is trifling with the subject, when he supposes conditions which never could occur 

 in nature in the case referred to. 



IV. — That the saltness of the sea is due to a rain of hydrochloric acid "flooding 

 the half cooled crust " with a highly heated acid deluge. 



This assumption requires no further comments than those included under the pre- 

 ceding head, where I have endeavoured to show that the whole of the chlorine did 

 not ascend into the atmosphere as hydrochloric acid, and, consequently, could not 

 flood the earth with the hot acid deluge insisted on by Dr. Hunt. 



V. — That the whole of "the calcareous strata, the marbles and various lime- 

 stones which we find on the earth's surface," have been precipitated from the 

 sea by carbonate of soda. 



Geologists have long agreed, that sedimentary limestones are the products of 

 the action of organic life; and microscopists, in confirming this, have further 

 proved that they do not possess the character of precipitates. Dr. Hunt evades 

 any reply to these objections, but asks a question in return, requesting to know 

 what becomes of the acid in case, as I contend, animals can utilize the salts of 

 lime contained in the sea. As is well known, sulphur plays a very importan 

 part in vital economy, entering both into the composition of organisms, and being 

 also given off as sulphuretted hydrogen in the gaseous form. I see, therefore, 

 many reasons for believing that animals do assimilate the sulphate of lime, which 

 we know is contained in such an enormous quantity in the ocean. 



VI. — That all the magnesian limestones and gypseous strata were formed in a 

 dense atmosphere of carbonic rxid. 



In 1H46, when in Birmingham, I was informed that for some years the manu- 

 facture of magnesian preparations was based upon the reactions of the compounds 

 of magnesia with carbonic acid, in a compressed atmosphere of carbonic acid. In 

 1849, Mr. Osborne, a gentleman connected with a si4»ilar manufactory in Ireland, 

 fully confirmed these statements, and shortly after the publication of Dr. Hunt's 

 paper in the Comptes Rendus, Dr. Lawson, in the course of conversation, ex- 



I 



ll 



1 



