289 



Dr. A. A. Hayes remarked that he had been much interested 

 in the theoretical considerations presented by Prof. Rogers. He 

 had long been aware that the conditions, belonging to deposits of 

 proto-carbonate of iron in the coal measures, are such as to for- 

 bid the supposition that the compound had been deposited from 

 waters holding the carbonate of iron in solution. The view pre- 

 sented, which refers the production of the carbonate from the 

 peroxide, by the reducing action of organic matter undergoing 

 changes in contact with it, harmonizes with a mass of chemical 

 facts and observations already accumulated. The native hydrated 

 peroxides of iron can be thus reduced to protoxides, and in part 

 converted into proto-carbonate of iron, in the laboratory, by the 

 aid of decomposing vegetable matter. In observing this change, 

 it is always found that the reducing action on the peroxide com- 

 mences at the time that the first steps in the decay of the organic 

 matter are observed. Carbonic acid gas, with carburetted hy- 

 drogen gas, appears at a later stage ; the protoxide of iron 

 formed being insufficient in quantity to combine with all the 

 carbonic acid which is produced. It is an essential condition in 

 this change that water, or moisture, be present ; as the organic 

 decomposition — a kind of putrefaction — would not otherwise 

 take place. It is proper in this connection to state the fact, that 

 the ferruginous springs of this country rarely contain carbonate 

 of iron dissolved. The iron salt which is present, is a crenate, 

 originating from the decomposition of organic matter, in contact 

 with ferruginous earth. The crenate of iron exists only as a 

 proto-salt ; it is soluble in water, and when brought in contact 

 with air, hydrate of peroxide of iron falls, usually containing 

 some humus, or coaly matter, resulting from the decomposition 

 of the crenic acid. It is not probable that the crenate can pro- 

 duce the carbonate of iron, if oxygen is present ; but when pro- 

 tected from oxidation, and especially in presence of an excess of 

 carbonic acid, the crenate may form a proto-carbonate of iron, as 

 the crenate of lime, even in the atmosphere, forms carbonate of 

 lime. 



In referring the production of carbonate of iron, deposited in 

 strata, to the solvent action of carbonic acid dissolved in mineral 



PROCEEDINGS B. S. N. H. VOL. V. 19 FEBRUARY, 1856. 



