550 DOMAIN VI. CARBONACEOUS. 



characters approaching to some serpentines; 

 for that peculiar odour does not arise from the 

 argil, as commonly supposed, but from the iron 

 contained in the argil, and therefore expires from 

 many rocks not argillaceous. It is worth obser- 

 vation, that serpentine has never been observed 

 to contain any metal except iron, and its rela- 

 tives pyrites and garnet ; so that it is not sur- 

 prising that it should contain graphite, or car- 

 buret of iron. Perhaps the superiority of the 

 English kind may be owing to this circumstance, 

 the unctuous nature of the rock imparting that 

 quality to the mineral ; as common flint becomes 

 menilite, from the unctuous and magnesian marl 

 in which it is deposited. 



Another rock is found at Borrodale, I know 

 not if in contact with the former, but it appears 

 somewhat allied from the structure and nodules. 

 This seems to be a magnesian felsite, of a dark 

 grey colour, dotted with little reddish crystals, 

 and with greenish nodules. It is well known 

 that the British rocks are often anomalous, or 

 transilient, and can scarcely be reduced to pre- 

 cise denominations, till the science shall have 

 made a far greater progress than it has at 

 present. 



of chamouni. Saussure discovered graphite, which, with the 

 writers of that time, he calls plombagine, on 



