I860.] w.u.t. — v]:xr.zri;i.\ and TTuxnun. \r,~ 



already elevated into the great range, was undergoing extensive 

 degradation during the tertiary epoch. The carbonaceous matter 

 associated with this upper group of the formation sometimes becomes 

 so abundant as to afford a fuel, admitting of exploitation : lignitic 

 deposits of this nature exist on the eastern coast of Trinidad, near 

 Racoon the Orinoco, and in the provinces of Barcelona and Coro. 



The only reliable data for estimating the thickness (viz. the coast- 

 sections in Trinidad) indicate not less than 4000 feet. The same 

 fossils seem to traverse the entire Beries, sonic of them belonging to 

 aviating species. The antiquity of the formation possibly ascends to 

 the mid-tertiary period, as the analogies with the anna of the Basin 

 of Vienna, and of the Faluns, seem to refer it to the Miocene horizon. 

 A striking contrast between the conditions prevailing in Trinidad 

 and on the main exists in the positions of the strata, which on the 

 continent are invariably horizontal or not exceeding 5°, whilst in 

 Trinidad they ;t re almost constantly highly inclined, often vertical, 

 and exhibiting the numerous violent but partial accidents which 

 have affected the system. 



Those singular substances termed porcellanites by the Qermans 

 (thermantides of Cordier) are "i common occurrence in the shaly 

 and carboniferous portions of the seriec in Trinidad, and are unques- 

 tionably attributable to the natural combustion of tin lignite and 

 vegetable de*bris diffused so generally in this formation. The result 

 of this process is to bake and indurate the contiguous Btrata for a 

 vertical extent of sometimes 7" to 80 feet, converting them into 

 Bubstanoes widely varying from their original condition. Thus the 

 clays present a material resembling extremely compact brick, and 

 aie brilliantly coloured by the anhydrous peroxide of iron. The 

 shales are still fissile, hut brittle and crowded with the impressions 

 of leaves and woody fragments sharply defined, whilst the siliceous 

 1m ds are usually transformed into a specii a "l porcelain-jasper. 



The asphalt of Trinidad is almost invariably disseminated in the 

 upper group of the "Newer Parian." When in situ, it is confined 

 to particular strata, which were originally shales containing a cer- 

 tain proportion of vegetable de*bris. The organic matter has under- 

 gone a special mineralization, producing bituminous, in place of the 



ordinary anthraciferons, Bubsl ition is not attribu- 



table to heat, nor of the nature of distillation, but is die to I hemical 



-11 at the ordinary temperature and under the norma] condi- 

 tions of the climate. The proofs that this fa the true mode of 

 generation of the asphalt rej noi onlj on tie- partial manner in 



w hich it is distributed in the strata, but also on UUmCTOUfl sjie, iuieiis 



of the vegetable matter in pi transformation and with the 



organic structure more <•] l< liter the removal by 



solution of the bituminous material, under the mi . remark- 



able alteration ion of the vegetable cells becomes 



which is not presented in any other form of the nuneralizati 

 wood * . A i" i uliarity attending the formation of the asphalt r. 



* I'nr the detail* of tin- tub the'H 



Appendix < ; on the aaphaltic d I Appeni 



■*a contribution on the (ban! p 



