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Show J THE l:A:rtTH .FCitMED .• West of England. The vast thickness of these beds, in some instances, is what attests the profoundness of the primeval oceans in which they were forme~; the Pe~nsy ~vanian gravvacke, a member of !he ~ext lug:hest senes, Is not less than a hundred miles In direct thickness. We have also evidence that the earliest strata were formed in the .presence of a stronger degree of heat than what operated in subsequent stages of the worl?, for. the laminre of the gneiss and of the mica and chlor1te scists are contorted in a way which could only b~ the result ?f a v~ry high temperature. It appears as If the seas In which these deposits were formed, had been in the troubled state of a caldron of water nearly at boil~ng heat. Su.c~ a condition would probably add not a little to the disintegra-ting power of the ocean. . The earliest stratified rocks contain no matters which are not to be found in the primitive granite. They are the same in material, but only changed into new forms and combinations; hence they have been called by Mr. Lyell, metamorphic rocks. But how comes it that some of. the~ are composed almost exclusively of one of the ma~enals ot granite; the mica schists, for example, of mica-the quartz rocks, of quartz, &c. ? For this there are ~oth chemical and mechanical causes. Suppose that. a. nv~r has a certain quantity of material to carry down, It IS evident that it will soonest drop the larger par.ti~les, ~nd carry the lightest farthest on. To auch a cause It Is owing that some of the materials of the worn-down granite have settled in one place and some in another.* Again, some of these matenals must be presumed to have been in a state of chemical solution iu the primeval seas. It would be, of course, in conforn1ity with chemical laws, that certain of these materials would be precipitated singly, or in modified combinations, to the bottom, so as to form rocks by themselves. The rocks hitherto spoken of contain none of those petrified 'reinains of vegetables and animals which abound so much in subsequently formed 1 ocks, and tell so w.ondrous a tale of the past history of our globe~ They ~Imply contain, as has been said, mineral materials denved from the primitive mass, and whiCh appear to have been formed into strata in seas of vast depth. The absence from these rocks of all traces of vegetable and animal life, Jt. Delabeche's Geological Researches. COMMENCEMENT OF ORGANIC Ll FE. 31 joined 1 o a consideration of the excessive temperature w'hich ~eems to have prevailed in their epoch, ha.s led to the inference that no plants or animals of any kind then existed. A few geologists have indeed endeavo1·ed 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 $Olidification, might have obliterated any remains 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. COMMENCEMENT OF ORGANIC LIFE-SEA PLANTS, CORALS, ETC. WE can scarcely be said to have passed out of these rocks, when 've 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 ofthe ingredients, carbonic acid gas, presents the element carbon, a perfect novelty in our progress. Whence this substance? The question is the more interesting, from our knowing that carbon is the main ingredient 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 of carbonic acid gas, forming the grand store from ":hi?h 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 rendered back to t~e atmosphere in their expired breath, so that its amount Is ne~er impaired. Knowing this, when we hear of carbon beginning to appear in the ascending series of ro~ks, we are ~navoidably led to consider it as marking a bme ,of some Importance in the earth's history, a new era ot natural |
