48 THE CANADIAN NATURALIST. [Feb. 



while Goeppert mentions its change into bitumen, and also observed 

 a resinous matter in the pores of silicified conifers. He found 

 tbat in some cases, as in certain agatized woods from Hungary, 

 the organic matter had almost, or altogether, disappeared, leaving 

 spaces which were empty, or filled only with water. Bead-like 

 drops of silica were occasionally found by him upon the bundles 

 of lio-neous fibres. He also observed in some cases an incrustation 

 of hyalite on the exterior of some specimens of silicified wood. 

 (Goeppert, Plantes Fossiles, livr. 1, pnrt 3.) 



The silicified woods from Antigua, unlike any of these described 

 by Goeppert, exhibit a replacement of the woody tissue by silica ; 

 some of them however still retaining portions of organic matter. 

 In a specimen of exogenous wood from that locality, which I have 

 lately examined with Dr. Dawsoa, the medullary rays are filled 

 with silica showing traces of cells, and the ducts are also filled with 

 silica. The whole of the woody fibre has moreover disappeared, 

 and its place is occupied by silica, which is distinguished by a 

 slight difference in color from that filling the place of the vessels. 

 In this case, it would appear that the process of silicifioatiou con- 

 sisted of two stages ; the first being the filhng up of the pores by 

 silica, followed by a removal, by decay, of the organic matter, 

 leaving a silicious skeleton like that of the Hungarian woods 

 noticed above, after which the empty spaces in this were filled by 

 a further deposition of silica. It is probable that processes similar 

 to those connected with silicification take place in the so-called 

 petrifaction of organic remains by carbonate and sulphate of lime, 

 sulphate of barytes, oxyd of iron, and metallic sulphurets. 



In this connection, may be mentioned the observations and ex- 

 periments of Peng>illy, Church, and others on the so-called Beek- 

 kite. This name has been given to mammillary chalcedonic 

 concretions around a nucleus of coral, sponge, shells, or even 

 of limestone, which occur i;i the Triassic conglomerates of Torbay 

 in England. This nucleus in some cases has disappeared, but in 

 others remains in greater or less part unchanged, or has been 

 partially silicified. These concretions apparently result from a 

 similar incrusting process to that which I have described in 

 Stromatopora and Metoptoma. Mr. Church has examined these 

 bodies with care both chemically and microscopically, and 

 in the L. E. & D. Phil. Magazine for February 1862 ([4], 

 xxiii, 95) has given his own and others' observations, with a 



