476 DOMAIN V. CALCAREOUS, 



is a Gothic castle half destroyed, here it presents 

 ruined walls ; in another place old bastions ; and 

 what still adds to the delusion is, that in these 

 sorts of natural paintings there exists a kind of 

 aerial perspective, which is very sensibly per- 

 ceived. The lower part, or what forms the first 

 plane, has a warm and bold tone ; the second 

 follows it, and weakens as it increases its dis- 

 tance ; the third becomes still fainter, while the 

 upper part, agreeing with the first, presents in 

 the distance a whitish zone, which terminates 

 the horizon, then blends itself more and more as 

 it rises, and at length reaches the top, where it 

 sometimes forms as it were clouds. 



" But approach close to it, all vanishes im- 

 mediately, and those pretended figures, which 

 at a distance seemed so well drawn, are converted 

 into irregular spots, which present nothing to 

 the eye. 



" This play of nature is owing to ferruginous 

 infiltrations in the fissures of this marble, which 

 otherwise is of a dull fracture, and very argil- 

 laceous; whence it is never used in architecture; 

 they merely make slabs of it, which are framed 

 like little pictures, and which are much esteemed 

 in commerce when of certain dimensions. It 

 sometimes occurs that the same slab is sawed in 

 two, and the parts are set together in the same 



