24 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. I. 



The vegetable remains comprise four species of pine, and 

 species of cedar, cypress, juniper, yew ; and of oak, poplar, 

 beech, ash, &c. ; and a few ferns, mosses, liverworts, con- 

 fervee, and fungi. The amber appears to have chiefly exuded 

 from the root-stock, but also from the bark and the wood, as 

 is the case with the Copal and Anime, which are resinous sub- 

 stances obtained from certain trees in India and America, 

 and largely employed for varnish : these resins are often sub- 

 stituted for true amber, especially when they contain insects, 

 &c.; but these are always of the existing indigenous species 

 of the country. There are many examples of copal and 

 anime, containing insects, placed in the case with genuine 

 fossil amber, for comparison. The difference observable in 

 the colour of the various species of amber, is attributable to 

 accidental chemical admixtures. 



Jet. This substance is so evidently wood in a carbonized 

 state (many species showing coniferous structure), that it is 

 only necessary to direct attention to the specimens in 

 dase 1. Some of the most productive beds of this fossil 

 in England are those in the Lias shale, near Whitby, in 

 Yorkshire. 



In this case there is an interesting example of Hessian 

 brown lignite passing into bituminous coal. 



Diamond. In Case 8 [4] there are many varieties of the 

 precious gem the diamond illustrating its varied colours 

 and crystalline forms ; among these are diamonds imbedded 

 in siliceous breccia, and in brown ironstone, and an octa- 

 hedral crystal with alluvial gold; and models of some 

 of the largest diamonds. The diamond, as is now gene- 

 rally known, is nothing more than carbon or charcoal in a 

 pure crystalline state ; of its vegetable origin there is no doubt. 

 At a heat less than the melting point of silver it burns and 

 is volatilized, yielding the same elementary products as char- 

 coal. By voltaic action it has been converted (by Jacquelin, 

 Faraday, Gassiott) into a substance possessing the appear- 

 ance, physical characters, and electrical properties of coke or 

 graphite, losing its insulating power, and becoming a conduc- 

 tor : its ordinary specific gravity is 3.368 ; when changed into 

 coke, 2.679. The diamond, like amber, is probably a vege- 

 table secretion, and has acquired its crystalline structure by 

 electro-chemical action. In Southern India and in the 



