Mlnerahgical Jccount of the Island of Corsica. 353 



tx) the magnificent orbicular granite of Corsica, the celebrity 

 of which is so well known. 



You may perhaps think I am exaggerating, but the fol- 

 lowing is the accurate description of the stone taken upon the 

 spot : 



The rock, the heart of which seems to be porphyroiclal, has 

 its paste composed of stony elements of a petro- siliceous 

 nature, irregularly disposed in small grains, in points and in 

 lineaments more or less rounded off, tying as it were with 

 each other, and varying in colour in proportion to the va- 

 rious degrees of alteration the ferruginous principle, which 

 is very abundant in this rock, has undergone : nevertheless 

 its general aspect, when seen at a certain distance, is the 

 reddish brown mixed with white spots shaded with red. 



It is in the midst of this paste that we observe regular 

 spheroidal bodies, from one to three inches in diameter, 

 scattered here and there at imequal distances, and imbedded 

 in the mass : the system of ibe formation of these kinds of 

 balls can only be considered as the result of a globulous cry- 

 stallization, which must have taken place rapidly; and not 

 like geodites, which would have been formed apart, and en- 

 veloped subsequently in a porphyritical substance. 



The method of crystallization in question is so far remark- 

 able, that we can form no idea of it except by representing a 

 circle into which a multitude of small stony bodies, oblong 

 and compressed, of a petro- siliceous nature, very close to 

 each other, must have been directed in radii, and as it were 

 from end to end, from the circumference towards the centre 

 of the circle, which gives them the appearance of divergent 

 radii; and there has resulted from it a globulous solid, 

 which with the hammer we may drive out from the place it 

 occupies, leaving a hole of its own form behind it. The 

 tendency of the crystallization has been such, that we see 

 around the spherical bodies in question, in the paste of the 

 stone, and round the spheres, the matter of the paste itself, 

 which, according to the tendency it had to approach it, has 

 formed a kind of aureolus, or zones, which surround several 

 of the bowls, which may be more easily remarked than de» 



Vol. 30. No. 120. May 1808. Z scribeds 



