DOMAIN XI. DECOMPOSED. 



destroyed. A single drop of sea water is 

 sufficient to produce the germ of destruc- 

 tion ; it forms a spot which gradually in- 

 creases, and spreads like a caries through 

 the whole mass of the stone : nor does it 

 stop there, but after some time affects all 

 the neighbouring stones in the wall. The 

 stones most subject to this malady are those 

 that contain most magnesia ; those which 

 are fine grained and of a close texture, resist 

 most/ Short as this account is, it appears 

 from it that the limestone of Malta con- 

 tains both calcareous earth and magnesia, 

 but most probably in a mild state ; and 

 the stone being of the looser kind, is of 

 the species which is known to contain most 

 mephitic air. M. Dolomieu shows, at the 

 end of his tract on the Lipari Islands, that 

 the atmosphere of Malta in some seasons, 

 when a south wind blows, is remarkably 

 fouled with mephitic air; and at other 

 times, when a north wind blows, remark- 

 ably pure ; and hence, of all others, most 

 fit for the generation of nitrous acid. 

 Again, sea water, besides common salt, 



