444 



Miscellaneous. 



their origin to a like cause ; that is, to a gradual deposition of silica, 

 from the silicate of potash decomposed by means of the carbonic 

 acid evolved during their decay. The infiltration and decomposition 

 of this salt would then give the coherence to the chalky beds which 

 they now possess. Indeed, to the infiltration of silicate of potash 

 may be ascribed the conversion into stone of all the argillaceous and 

 calcareous deposits ; assisted, of course, by heat. 



I am well aware that the supposition which we have advanced has 

 to encounter a very serious objection in the paucity of vegetable re- 

 mains found in these beds; but this objection is by no means conclu- 

 sive against the opinion. The plants found in them are all marine, 

 and from their perishable nature could not be accumulated in quantity. 

 Besides, the loose nature of the deposit would long admit of the access 

 of water, which would ensure their decomposition. This circumstance 

 must be allowed its due importance ; for the impermeability to 

 water in chalky beds is vastly inferior to that of arenaceous and 

 argillaceous deposits ; and the experiments of Dr. Lindley have prov- 

 ed that long immersion in water destroys most plants. Allow, 

 then, even this suggestion as a partial cause (but we see no obstacle 

 in assuming it as the universal one), and there is no difficulty in 

 accounting for the withdrawal of carbonic acid from the atmosphere 

 during the deposition of the cretaceous beds. In consequence of this 

 withdrawal, the atmosphere becomes fitted to sustain higher forms 

 of organic life, and these accordingly sprung into being during the 

 tertiary period. During the tertiary period itself, this withdrawal 

 of carbonic acid from, and supply of oxygen to, the atmosphere, 

 was constantly proceeding, as the vast beds of lignite on the Rhine 

 amply testify ; and a gradual increase of forms of animal life is ac- 

 cordingly observed, from the basis of the tertiary rocks, to the sum- 

 mit of the series. It would be desirable that more conclusive 

 evidences were furnished of the age of the brown coal : in absence 

 of information to determine to what part of the series it should be 

 placed, we must keep from drawing conclusions regarding it ; the 

 general inference, however, may be drawn, that these entombed 

 lignites do certainly not belong to the newer part of the series. 



Although we find very many species in the tertiary strata similar or 

 identical with those now inhabiting the earth, still neither in these nor 

 in the post tertiary or alluvial deposits, do we find any trace of man 

 or of his works. But previous to his creation it became indispensa- 

 ble that a balance should be established between animal and vegetable 

 life. It was the commencement of a grand era that ushered into the 



