78 OF THE INORGANIC CONSTITUENTS OF PLANTS. 



less the many hundred tons annually brought from Italy as an 

 article of commerce, are procured by the uninterrupted accu- 

 mulation of this apparently inappreciable quantity. The hot 

 steam issuing from the interior of the earth, passes through cold 

 water in the lagoons of Castel Nuovo and Cherchiago ; in this 

 way the boracic acid is gradually accumulated, till at last it may 

 be obtained in crystals by the evaporation of the water. It is 

 evident, from the temperature of the steam, that it must have 

 come out of depths in which human beings and animals never 

 could have lived, and yet it is very remarkable and highly 

 important that ammonia is never absent from it. In the large 

 works in Liverpool, where natural boracic acid is converted into 

 borax, many hundred pounds of sulphate of ammonia are obtained 

 at the same time. 



This ammonia has not been produced by the animai or, 

 ganism, but existed before the creation of human beings, 

 being a part, a primary constituent, of the globe itself. 



The experiments instituted under Lavoisier's guidance by the 

 Direction des Poudrcs et Salpetres, have proved that during the 

 evaporation of the saltpetre ley, the salt volatilizes with the water, 

 and causes a loss which could not before be explained. It is 

 known also that, in sea-storms, leaves of plants in the direction 

 of the wind are covered with crystals of salt, even at the dis- 

 tance of from 20 to 30 miles from the sea. But it does not 

 require a storm to cause the volatilization of the salt, for the air 

 hanging over the sea always contains enough of this substance 

 to render turbid a solution of nitrate of silver, and every breeze 

 must carry this away. Now, as thousands of tons of sea-water 

 annually evaporate into the atmosphere, a corresponding quantity 

 of the salts dissolved in it, viz., of common salt, chloride of potas- 

 sium, magnesia, and the remaining constituents of the sea-water, 

 will be conveyed by wind to the land. 



This volatilization is a source of considerable loss in salt- 

 works, especially where the proportion of salt in the water is 

 small. This has been completely proved at the salt-works of 

 Nauheim, by the very intelligent director of that establishment, 

 M. Wilhelmi. He hung a plate of glass between two evaporat- 

 ing houses, distant about 1200 paces from each other, and found 



