107 



(kaolin) of Mori, to porphyry of red sandstone. 

 Analogous chemical actions may take place in 

 primitive and transition slates, as well as in 

 tertiary formations. All slates, and this fact is 

 very important, contain near five per cent of 

 potash, sulphuret of iron, peroxid of iron, car- 

 bon, &c. The contact of so many humected 

 heterogeneous substances must necessarily lead 

 them to a change of state and composition. The 

 efflorescent salts, that abundantly cover the 

 aluminous slates of Robalo, indicate how much 

 these chemical effects are favoured by the high 

 temperature of the climate ; but, I repeat, in a 

 rock where there are no crevices, no vacuities 

 parallel to the direction and inclination of the 

 strata, native alum, hemidiaphanous and of con- 

 choid fracture, completely filling it's place (it's 

 beds), must be regarded as being of the same 

 age with the rock in which it is contained. The 

 term contemporary formation is here taken in 

 the sense attached to it by geognosts, in speak- 

 ing of beds of quartz in clay slate, granular lime- 

 stone in micaslate, or feldspar in gneis. 



After having for a long time wandered over 

 barren scenes, amid rocks entirely destitute of 

 vegetation, the eye reposed with pleasure on 

 tufts of malpighia and croton, which we found 

 in descending toward the coast. These ar-> 

 borescent crotons were of two new species *, 



* Croton argyrophyUus, and c. marginatus. 



