1SS MR « hatchett's observations 



Component By this analyfis, 250 grains of the fchiftus afforded, 



P am - Grains. 



Water ... A. - 42.50 



Thick brown oily bitumen 7 R J 7.50 



Mixed gas (by computation) j ' \ 23.75 



Charcoal (by computation) C. - 54.25 



Silica - - - - D. - 98 



Oxide of iron - E. - 6 



Alumina - - - - F. - 15 



247. 



But the water and vegetable matter mutt be regarded as extra- 

 neous ; and, if they are deducted, the real compofition of the 

 fchiftus is nearly as follows. 

 Its component Silica - 82.30 



parts, exclusive at- , ^ ^ ■, 



5f water and Alumina -.- - - 12.61 



vegetable matter. Oxide of Iron - - 5. 



99.91. 

 It evidently, therefore, belongs to the family of argillaceous 

 fchiftus, although the proportion of filica is more confiderable 

 than has been found in thofe hitherto fubjecled to chemical 

 analyfis. 



The fchiftus has not been noticed by von Troil, nor by any 

 of thofe who have written concerning Iceland ; for the flate 

 which was fent to Profeffor Bergmann by the former, and 

 which is mentioned by the latter in one of his letters, is there 

 exprefsly ftated to be the common aluminous flate containing 

 impreflions *. 



§ IV. 

 Queftion, From the experiments which have been related, we find that 



whether the Ujg i eaves contained in (he Iceland fchiftus, although they are 

 circumftances or 



of'thTkhlftu" * Letters on Iceland > b y Uno von Troil > p- 355 - 



were peculiar. Mr. Faujas St. Fond has however defcribed a fchiftus nearly 



fimilar, which is found near Roche-Seauve, in the Vivarais # 

 The,ftratum extends about two leagues ; and the only difference is, 

 that, according to Mr. St. Fond, the fchiftus at Roche-Seauve is of 

 the nature of marble, or, as he terms it, argillo-calcareous, 

 whereas this of Iceland is ubdoubtedly argillaceous. From Mr. 

 St. Fond's account, it does not appear that the vegetable leaves 

 contained in the fchiftus of Roche-Seauve have been chemically 

 examined. EJfai de Geologic, par. B. Faujas St. Fond, Tome I- 

 pp. 128 and 134. 



apparently 





