474 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



was in strict accordance with the known chemical laws, and flowed 

 logically from the hypothesis of the ingeneous origin of our 

 phmet. The early ocean should thus abound in salts of lime and 

 magnesia, and this is confirmed by the saline waters from the 

 Paleozoic rocks, wiiich represent fossil sea water of that ancient 

 period. Dr. Hunt here referred to his extended chemical and 

 physical investigations of the older rocks and their mineral springs 

 in support of this view. 



The stronger acids of chlorine and sulphur having been sepa- 

 rated from the atmosphere, a decomposition of the silicates of the 

 exposed portion of the earth's crust under the influence of carbonic 

 acid moisture and heat went on, resulting like the modern process 

 of kaolinization in the production of a silicate of alumina or clay 

 and carbonates of the protoyed basis. In this way great quanti- 

 ties of carbonate of soda were formed, which, decomposing the 

 lime and magnesia salts of the sea, gave rise to the first limestones 

 and to chloride of sodium. Hence the clays, the limestones, and 

 the sea salt were the joint results of a process which was slowly 

 removing from the earth its carbonic acid and fitting it for the 

 support of higher forms of life. These views of Dr. Hunt, first 

 put forward in 1858 and 1859, are gradually being received and 

 appropriated by Avriters who do not alwa^'-s acknowledge the 

 source of them. They are here insisted upon as preliminary to 

 some considerations on the atmosphere of early lines, when it 

 must have contained in the form of carbonic acid the whole or the 

 oreater part of the carbon now present in the limestone strata of 

 the earth and in the beds of fossil coal. 



Simple calculations show that the carbonic acid contained in a 

 layer of pure carbonate of lime extending over the earth with a 

 thickness of 8.31 meters, would, if sot ft-ee, double the weight of 

 our atmosphere, and that from 13.65 meters (about forty-four feet), 

 would double its volume. It moreover appears that a similar 

 layer of ordinary coal, one meter in thickness, would suffice to 

 convert into carbonic acid the whole of the oxygen of the atmos- 

 phere, so that if, as is probable, the whole amount of coal and 

 carbonaceous matters on the earth exceeds this quantity, there 

 must have been an absorption of the oxygen, set free during the 

 conversion of carbonic acid into coal, this oxygen being probably 

 retained by peroxyd of iron. Disregarding this, however, and 

 admittino- that the carbonic acid, corresponding to a layer 8.61 

 meters of limestone (about twenty-eight feet) wei-e present in our 



