56 



alkalescent, continues in the same state through- 

 out the year, and is constantly^ covered with a 

 very fine verdure that attracts the animals, who 

 are frequently mired and perish in it; while 

 that of Sweden inclines to an acid, swells much 

 in certain seasons, and is naturally barren. 



The fourth kind is the rovo (argilla rovia) 

 from which the inhabitants procure an excellent 

 black ; it is used in dying* wool, and represented 

 by Feuille and Frazier as superior to the best 

 European blacks. This clay is of a very fine 

 grain, of a deep black, a little bituminous, and 

 very vitriolic. It is found in almost all the 

 forests, and has the property of communicating 

 to pieces of wood that are buried in it for a short 

 time, a sort of black varnish, very shining and 

 durable. The colour is obtained by boiling the 

 clay with the leaves of a plant called the pankc 

 tinctoria, hereafter described. 



They grey clay, which is the fifth species, 

 posseses all the properties requisite for pottery. 

 It appears to be of a kind suitable for retorts, 

 crucibles, &c. as the vessels that I have seen of 

 it are very strong, and capable of resisting the 

 most violent fire. 



Among the calcareous earths is a kind of lime 

 or gravelly chalk, found in the Cordilleras, in 

 quarries of many miles in extent, and of a depth 

 hitherto unexplored. I have given it the name 

 of volcanic lime (calx vulcanica) as I am con- 



