1864.] SILICIFICATION OP FOSSILS. 49 



number of figures. He has also described in this paper the 

 results of some experiments on the process of silicification ; for 

 further details of which see The Chemical N"ews, vol. v, 95. Mr. 

 Church prepared a solution of silica in water by dialysis, accord- 

 ing to Graham's method (L. E. & D. Phil. Mag. [4], xxiii, 295), 

 and found that when this solution, containing about one two-hun- 

 dredths of silica, and impregnated with a little carbonic acid, was 

 filtered through fragments of coral, a large portion of carbonate 

 of lime was dissolved, an J the whole of the silica removed. Similar 

 results, though to a less extent, were obtained with shells. In 

 another experiment, a fragment of a recent coral was fitted into 

 the neck of a funnel, and a solution prepared as above, with a 

 little carbonic acid, and containing one hundredth of silica, was 

 allowed to drop on the coral, and after slowly filtering through, 

 was found, as in the previous experiment, to have abandoned the 

 whole of its silica, while the coral had lost nearly all its lime, 

 although retaining its structure in a great measure. It was however 

 covered with a thick film of gelatinous silica.'' Mr. Church farther 

 observed that the addition of small portions of the solid carbonate 

 of lime, barytes, or strontia to a strong solution of pure silica, caused 

 it to gelatinize immediately; and according to Graham, solutions of 

 these carbonates have the same efi'ect. The concentric structure 

 which is characteristic of chalcedony, was observed by Mr. Church 

 in the silicious deposits from the Geysers of Iceland, and from the 

 hot springs of Luzon in the Philippine Islands, as well as in meni- 

 lite; and Mr. J. H. Gladstone, in a note to Mr. Church, in the 

 paper already cited from the Philos. Magazine, refers to a similar 

 structure as having been observed by Mr. Rainey in carbonate of 

 lime formed in animal tissues : it is also artificially obtained 

 when carbonate of lime is slowly deposited in the presence of 

 gum or albumen. Mr. Church has since described (Chera. 

 News, vi, 306) a curious example of the deposition of silica. A 

 basket of eggs was recently found in a chalk-pit near Winche&- 

 ter, where it had been buried beneath the broken rock for, it is 

 supposed, four or five centuries. The organic matter and the cal- 

 careous shell of the eggs ha 1 both disappeare 1, their places being 

 occupied by chalcedony ; " which seemed farther to have been de- 

 posited upon the willow twigs composing the basket, incrusting it 

 so well that the real nature of the latter is evident to this clay." 

 I have thoucrht it well to brinfj toorether these observations 



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