Gi Observatiuns on the Petrifaction of Shells 



beds which are constantly precipitated, and envelop the living shells, 

 compose agglomei-ations which harden so rapidly as to admit of being 

 employed tor building. These stones are even much sought after, on 

 account of their lightness and solidity : they have the advantage of 

 resisting the action of projectiles without cracking, balls sinking into 

 them. 



The shelly sandstones of geological times have their analogues, not 

 only in those produced in our own day in the Mediterranean, but 

 also in the siliceous banks formed on the shores of the ocean. M. 

 De la Beche cites a very remarkable example of this on the north 

 coast of Cornwall. These sandstones are so solid that, in a steep 

 shore which is formed of them, they have dug out caverns at New 

 Park to afford shelter during embarkation. They have even built 

 the church of Crantoch, which is very near, of this material. 



Banks of pudding-stone, so numerous and extensive in geological 

 times, are still forming in the present day. One in particular is 

 mentioned between Dives and the mouth of the Ornc. There is a 

 vast collection of rolled pebbles, mingled with shells which have still 

 the freshness of living species. These agglomerations are cemented 

 with carbonate of lime, formed in part by the triturated debris of 

 some of these shells, as MM. Constant Prevost and Huot have ob- 

 served. In like manner, siliceous sediments are deposited every day 

 from mineral springs in an indefinite number of places. These sedi- 

 ments correspond to similar deposites of geological times. 



Modern travertins remind us in every respect of the travertins of 

 geological epochs. The former form layers as distinctly stratified as 

 the latter, which shews, as Mr Lyell remarks, that they have been 

 produced by the same cause. 



No doubt these facts are insufficient to pi'ove that all the pheno- 

 mena of the old world are continued in the present day, but they 

 are calculated to make us presume so in regard to the majority of 

 such as are best known to us. Now, it is rational to suppose that 

 such also must be the case with respect to those facts to which we 

 have not yet directed our attention. It is then extremely probable 

 that the same laws have always regulated physical phenomena, to 

 whatever epochs they belong, for unity has been at all times the es- 

 sential character of the works of Nature. 



Conclusions. 



The facts we have stated lead to the following conclusion : — 



1st, Shells which have lain for a long time in the Mediterranean 

 petrify there, just as they petrified in the basin of the ancient seas. 



'2d, The fossilization of the shells of the old world, and the petri- 

 faction of shells in the basin of existing seas, were effected in the 

 same manner, and constitute two similar phenomena. 



Sd, The petrified shells of the old world, and those now met with 

 in the same state on the shores of the Mediterranean, are almost 

 identical in regard to their chemical composition. 



