44 Olservations an ("he Change of 



^vhen longitudinally divided, the whole surface constantly 

 presents a series of the leaves which have been mentioned, 

 unitormlv spread, and commonly of a light gray on the 

 upper surface, and of a dark brown on the other ; the fibres 

 on the li<rht grav surface being generallv of a blackish- 

 broxvn, which is also the colour assumed by the schistus 

 when reduced to powder. 



The leaves appeared to be in the state of charcoal, by being 

 extremely brittle, by the blackish brown colour, by defla- 

 gratimj with nitre, by the manner of burning, and bv form- 

 iiijr carbonic acid. I was, however, soon convinced that 

 the substance of these leaves was not complete charcoal, 

 but might more properly be regarded as vegetable matter in 

 an incipient state of carbonization, which, although pos- 

 sesseil of manv of the apparent properties of charcoal, still 

 retained a small portion of some of the other principles of 

 tl)c orioinal Tcgetable. 



i\}v suspicion was excited, partly by the odour produced 

 dv\rin<r combustion, which raiher more resembled that of 

 unml than that of charcoal, and partly bv the brown solu- 

 tion formed bv disicstme the powder of the imburned 

 schistus in boiling distilled water; for by various tests 1 

 ascertained that the substance thus dissolved was not of a 

 mineral nature. In order, however, fully to satisfy myself 

 m this respect, I digested 250 grains of the pulverized 

 srhistus with six ounces of water. 



'j'he liquor was, as before, of a dark brown colour. 



]t had but little flavour. 



Pnissiate of potash, muriate of barytcs, and solution of 

 isinjrl-ass, did not produce any eficct; nitrate of silver formed 

 k v^iP,- famt cloud ; sulphate of iron was slowly precipitated, 

 of a (lark brownish colour; and muriate of tin produced a 

 while precipitate. 



A portion of the solution, bv long exposure to the air, 

 was partially decomposed ; and a quantity of a brown sub- 

 ,-ianee was deposited, which could not again be dissolved 

 in water. 



Another portion was also evaporated to dryness, and 

 ritforded a similar brown substance, which was only par- 

 Hallv soluble in water ; and the residuuiti, in both of the 

 above cases, was found to be insoluble in alcohol and in 

 rther. 



When burned it emitted smoke with the odour of vege- 

 table matter. 



ilM) srrains of the schistus afforded about three grains of 

 the above substance ; and, when the properties of the 



aqueous 



