which accompany the Boracic Acid in the Lagoons of Tuscany. 285 



In one single locality, boracic acid occurs in solution in a 

 true small lake, which is actually called Lago. 



M. de Larderel, the proprietor of the boracic acid works, has 

 recently caused to be made artesian borings which have fur- 

 nished him with boiling waters, accompanied by the same gaseous 

 emanations and holding in solution boracic acid to an amount 

 at least equal to that of the waters of the lagoons. They rise 

 to a considerable height (about 20 metres) at the moment 

 when the borer meets with them, and cause an eruption of muddy 

 matters and stones which recall the phsenomena of the Geysers of 

 Iceland. 



The tertiary soil, in the midst of which these emanations break 

 forth, consists of a compact limestone with spathic veins called 

 aJberese, converted into gypsum in many localities, of micaceous 

 grit called macigno, and schistose clays. 



The triangular space comprised within these various ema- 

 nations is included between the culminating points of Monte 

 Catini, Monte Calvi, and the mountain Gerfalco. The soil is 

 traversed at several points by masses of serpentine. 



In the course of the autumn of 1857, being encouraged by 

 the kind offers addressed to us by the Count de Larderel, whose 

 recent loss we have to deplore, we made our preparations for a 

 journey into Tuscany. We started provided with all the appa- 

 ratus necessary either to collect the gases, or to execute upon 

 the spot a series of experiments and summary analyses. 



In a letter to M. Elie de Beaumont, dated Pomarance, No- 

 vember 1857*, we have already announced some results of the 

 first experiments made upon the spot. In particular we indi- 

 cated the existence, in the gases, of a combustible hydrocarbu- 

 retted mixture free from oxide of carbon, and also the absence 

 of oxygen ; this last fact was in accordance with the observations 

 of Professor Schmidt. 



In the memoir which we have now the honour to present to 

 the Academy, and which is the fruit of the labours of several 

 months, we treat only of our investigation of the gaseous products, 

 reserving for a second communication the results of experiments 

 made upon the condensed liquid products, upon the difibrent 

 products arising from the alteration of the rocks in contact with 

 the emanations, and upon the mother-liquors of the lagoons f. 



* Comptes Reiidus, vol. xlv. p. 750. 



t Although this first memoir relates particularly to the analyses of the 

 gases, there is a question rej^arding the production of l)oracic acid which 

 we desired to elucidate at tlie outset, and of which it appears to us indis- 

 pensable to furnish the solution. 



The presence of boracic acid in the emanations of gases and vapours has 

 been doubted of late years ; it has been necessary therefore to have recourse 

 to complicated explanations to account for the presence of boracic acid in 



