Ch. XI. SOUTH AMERICA. 477 



It muft be obferved, that the rocks and all the 

 parts which this river waflies, are covered with a 

 x:ruft of a hardnefs little inferior to that of the main 

 rock ; and this increafes its volume, and diftinguilhes 

 itfelf from the original rock, which is lomething 

 yellowifh. The inference I would draw from hence 

 js, that the water of the river is mixed with petri- 

 fying, vifcid, and glutinous particles, which adhere 

 to the body they furround : and as by their extreme 

 \ fubtility they infmuate themfelves through its pores, 

 they fill the place of the fibres, which the w^ater in- 

 fenfibly rots off and feparates, till at length all that 

 was leaf or wood gives way to that petrifying mat- 

 ter ; which ftill retains the imprefiion of the parts 

 of the original, with its feveral veins, fibres, and 

 ramifications. For at the time of its infinuation, the 

 diids of the wood, or leaves, ferve for a kind of 

 mould, by which it naturally takes the entire figure 

 of the body into which it has obtruded itfelf. 



An obfervation I made with fomc branches con- 

 firms me in this opinion : for having opened them 

 I found fome leaves and bits of wood, which fnappe4 

 on breaking *, -and the infide was as large as real 

 ftone, the texture only remaining of its firft fub- 

 llance. But in others, the parts confolidated by the 

 Hony matter lhapped *, and the fibres, not having yet 

 undergone a total corruption, retained the appearance 

 of wood, though fome were more rotten and decayed 

 than others. 1 had alfo fome leaves, the furface of 

 which was only covered with a very fine lapideous te- 

 gument, but within were entire leaves, except here and 

 there a little mark of decay. 



It is to be obferved, that this matter much 

 more eafily failens on any corruptible fubftance, 

 than on the more compa6t and folid, as Hones 

 and the like : the reafon of which is, that in on« 

 it meets with pores, ip which it fixes itfelf; but 



having 



