S07ne of the Principles of Figetables Into B'dumen. 

 By this analysis^ 230 grains of the schistus afforded, 



' Water - - - 



Thick brown oily bitumen 

 Mixed gas (by computation) 

 Charcoal (by computation) 

 Silica _ _ _ 



Oxide of iron 

 Ahunina - _ _ 



247. 

 But the water and vegetable matter must be regarded as ex- 

 traneous ; and if thev are deducted, the real composition of 

 the schistus is nearly as follows. 



Silica - - 82.30 



Alumina - - 12.61 



Oxide of ircJn - 5 



99.91 



It evidently, therefore, belongs to the family of argillaceous 

 schistus, although the proportion of silica is more consi- 

 derable than has been found ia those hitherto subjected to 

 chemical analysis. 



This schistus has not been noticed by von Troil, nor by 

 any of those v.ho have written concerning Iceland ; for the 

 blale which was sent to Professor Bcrgmaun by the former, 

 •.nd which is mentioned by the latter in one of his letters, 

 is there expressly staled to be the conimun aluminous slate 

 containing impressions *. 



§ IV. 

 From the experiments which have been related, we find 

 tliat the leaves contained in the Iceland schistus, although 

 ihcy are apparently reduced almost to the state of charcoal, 

 ijcverthekss retain some part of their original proximate 

 principles; namely, extract and resin. Ihis, of itself, is 



• Letters on Iceland, by Uno von Troil, p. 355, 



Mr. Faujis St. Fond lias, however, (le-<cribcd a tchistvis nearly simi- 

 lar, whicli is found ncjr Rochc-Seauve, in the Vivarais. The stratum 

 extends about two lca}<ucs ; and the only diflerence is, that, according 

 to Mr. St. Fond, die schistu-. at Roche- bcauvc is of the nature of marie, 

 or, as he terms it, argillo-calcareous, wiiereas this of Iceland is undoubt- 

 tdly argillaceous. From Mr. St. Pond's account, it does not appear 

 that the vetaiablc leaves contained in the schistus of Rochc-Se^uvc have 

 been ch<.-niicallv examined. E:iai de Gio^j^'w, par B. Faujas St. Fond, 

 tome i. pp. ii£ and > >,\. 



3 undoubtedly • 



