DOMAIN XI. DECOMPOSED. 217 



by its property of forming nitrous acid, 

 when, during its nascent state, it is gra- 

 dually brought into contact with the oxy- 

 gen of the atmosphere, in a moderately 

 dry state, may also promote decomposi- 

 tion ; calcareous stone are known to con- 

 tain it in pretty considerable proportion, 

 and those that contain animal remains, pro- 

 bably most ; from this consideration we 

 may derive some explanation of a very re- 

 markable phenomenon, related by M. Do- 

 lomieu 36* Roz. 116. 'All the houses of 

 Malta are built of a fine grained limestone, Limestone of 



Malta. 



of a loose and soft texture, but which 

 hardens by exposure to the air. There is 

 a circumstance which hastens its destruc- 

 tion and reduces it to powder, namely, 

 when it is wetted by sea water; after this 

 it never dries, but is covered by a saline 

 effervescence ; and a crust is found some 

 tenths of an inch thick, mixed with com- 

 mon salt, nitre, and nitrated lime ; under 

 this crust the stone moulders into dust, the 

 crust falls off, and other crusts are suc- 

 cessively formed, until the whole stone is 



