FOREIGN CORRESPONDENCE. 



525 



that of the carbonic acid gas (if we consider the maximum) as 6*4 : 93'6 

 — oxygen appears to be completely absent. Nitrogen, on the con- 

 trary, is always present, in the proportion of from 2 to 3 per cent. 



3, and finally, comes a fact which M^^tT. Ch. Deville and Leblanc 

 have been the first to observe : In every case these gaseous mixtures 

 contain a certain quantity of free hydrogen gas and protocarbide of 

 hydr »gen (C^ H ) which both measured together attain, on an average, 

 the same per-centage as the nitrogen. In some places, for instance, in 

 a crack or fissure that joins Laderello and Castelnuovo, the proportion 

 between these two combustible gases is nearly as 1 : 1. 



The presence of hydrogen in these gaseous emanations of Tuscany 

 affords a new feature of resemblance between them and the famous 

 Geysers and Solfatara of Iceland, but up to the present time we are 

 not aware that any of the acute observers who have studied the Iceland 

 emanations have ever remarked in them the presence of carburetted 

 hydrogen. 



Closing the memoir quoted above, we will add here a few remarks 

 upon boracic acid, as it is a very interesting natural production. 

 Eefore it was discovered dissolved in the waters of the Tuscan lagoni, 

 all the iorax used in metallurgical operations, in medicine, and by the 

 mineralogist in his essays with the blow-pipe, came from Asia — prin- 

 cipally from India. Xow, the boric acid of Tuscany is converted into 

 borax (bi-borate of soda), for the arts and manufactures. The natural 

 acid only contains 56 per cent, of pure acid, the remainder being 

 water. 



Boric acid (or boracic acid, as it is often called), though not volatile 

 when pure, even at a high temperature, possesses the peculiar property 

 of being volatile in watery vapour ; so that, if a dissolution of it be 

 distilled in a retort, a certain quantity of the acid will be found to have 

 passed over with the steam, and will slowly deposit itself in the reci- 

 pient, where it will crystallize in beautiful little white crystals. This 

 is pretty nearly what takes place in nature. Besides the invisible 

 vapour with which the air is constantly more or less charged, and which 

 is every now and then condensed in the shape of clouds or fog, there is 

 a constant supply of watery vapour, that makes its way (together 

 with the gases of which we have been speaking above), through the 

 fissures of certain rocks, either volcanos, solfatara, or calcareous and 

 serpentine formations. These vapours are evolved from the earth near, 

 at, or above boiling point (100° centigrade), with a hissing noise, and 

 sometimes from high white columns of steam, that are visible from 

 afar. This is the phenomenon to which the Italians have given the 

 name of fumaroJla, and which is nowhere more strikingly grand than 

 in Tuscany, in the calcareous hills (often associated with serpentine) 

 of Monte- Cerboli, Castelnuovo, and Monte-Rotondo. 



This projected vapour carries with it boric acid and the gases noticed 

 above. The vapours rise either directly from clefts in the rocks or 

 from stagnant pools, in which they throw up small cones of mud ; in 

 places where the boric acid vapours permeate the fissures of the rocks, 

 they, deposit sulphur. The boric acid is dissolved by the water, which 

 constantly condenses from the fumarolle, and forms the lagoni, from 



