COMMENCEMENT OF ORGANIC LIFE. 31 



joined to a consideration of the excessive temperature 

 wliich seems to have prevailed in their epoch, has led to 

 the inference that no plants or animals of any kind then 

 existed. A few geologists have indeed endeavored to 

 show that the absence of organic remains is no proof of 

 the globe having been then unfruitful or uninhabited, as 

 the heat to which these rocks have been subjected at the 

 time of their solidification, might have obliterated any re- 

 mains of either plants or animals which were included 

 in them. But this is only an hypothesis of negation ; 

 and it certainly seems very unlikely that a degree of heat 

 sufficient to obliterate the remains of plants or animals 

 when dead, would ever allow of their coming into or 

 continuing in existence. 



COMMENC EMENT OF ORGANIC LIFE— SEA 

 PLANTS, CORALS, ETC. 



We can scarcely be said to have passed out of these 

 rocks, when we begin to find new conditions in the earth. 

 It is here to be observed that the subsequent rocks are 

 formed, in a great measure, of matters derived from the 

 substance of those which went before, but contain also 

 beds of limestone, which is to no small extent composed 

 of an ingredient which has not hitherto appeared. Lime 

 stone is a carbonate of lime, a secondary compound of 

 which one of the ingredients, carbonic acid gas, presents 

 the element carbon, a perfect novelty in our progress. 

 Whence this substance ? The question is the more inte- 

 resting, from our knowing that carbon is the main ingre- 

 dient in organic things. There is reason to believe that 

 its primeval condition was that of a gas, confined in the 

 interior of the earth, and diffused in the atmosphere. The 

 atmosphere still contains about a two-thousandth part ot 

 carbonic acid gas, forming the grand store from which the 

 substance of each year's crop of herbage and grain is de- 

 rived, passing from herbage and grain into animal sub 

 stance, and from animals again rendert I back to the atmo- 

 sphere in their expired breath, so that its amount is never 

 impaired. Knowing this, when we hear of carbon begin- 

 ning to appear in the ascending series of rocks, we are 

 unavoidably led to consider it as marking a time of some 

 importance in the earth's history, a new era ol natural 



