58 ON THE FORMATION OF LIMESTONE BEDS. 



the encrinites, while the other equivalent of carbonic 

 acid gas was given off to the atmosphere ? 



89. If so, was it during the formation of the 

 enormous beds of mountain limestone, when the bi- 

 carbonate of lime, according to the process we have 

 described, was reduced to a carbonate, that the sur- 

 plus carbonic acid gas, which would thus be given 

 off to the atmosphere of the carboniferous period, 

 would be fully adequate to provide for the growth 

 of the luxuriant vegetation of that period ? 



90. How is it that the limestone which occurs in 

 primitive rocks seldom consists of extended beds, 

 but is found in lumpish masses that are included in 

 those rocks ? Is it from this cause the primitive 

 limestone was deposited in shallow water, when 

 the ocean enveloped the whole globe ; and because 

 of this, when carbonic acid gas escaped from a 

 fissure at the bottom of the ocean, the pressure of 

 the superincumbent waters was not such as to cause 

 the carbonic acid gas to combine with the lime in 

 solution to form a bi-carbonate, but a carbonate of 

 lime ? There would be thus little or no lateral dif- 

 fusion, as the carbonate of lime, when formed, would 

 be immediately precipitated, and thus lumpish 

 masses of limestone would be formed, and not ex- 

 tended beds. 



