384 MM. Deville and Le Blanc on the Gaseous Emanations 



Vt'^s.m^d-q^ dq q dq _ dt 



sin^^ dO sin^ 6'^0 #* 



For any given form of t, therefore, the problem reduces itself 

 to the integration of either of these linear, partial, diflereutial 

 equations, for, of jo and q, one being known the other is imme- 

 diately deduced, and 



u='^{pd6-\-qd(l)). 



Here, however, p and q involve arbitrary functions of and <p, 

 which must in general be particularized before the final inte- 

 gration can be effected. 

 Paris, July 1858. 



XXX. On the Gaseous Emanations ivhich accompany the Boracic 

 Acid in the Lagoom of Tuscany. By C. Sainte- Claire 

 Deville and F. Le Blanc. — First Memoir*. 



AMONGST the geological phsenomena which give rise to 

 evolutions of gases and vapours thrown into the atmo- 

 sphere at a high temperature, there are scarcely any which merit 

 in a higher degree to fix our attention than those emanations 

 which, in Tuscany, annually bring to the surface of the soil 

 enormous quantities of boracic acid. 



These phsenoniena have already been described by several 

 naturalists and geologists, especially by Targioni-Tozzetti, 

 Coquand, &c, ; and in a chemical point of view tlicy have been 

 the object of investigation on the part of M. Payen, and latterly 

 of M. Schmidt, Professor at Dorpat. 



In the locality, as is well known, the name of soffioni is given 

 to impetuous currents of gas and aqueous vapour at a high tem- 

 peratm-e, forcing a passage for themselves into the atmosphere 

 after having overcome the resistance of the soil, which finally 

 loses its cohesion. 



When the evolution takes place in the interior of cavities 

 filled with water, the name of layoni is given to these accidental 

 basins, which become the seat of a constant ebullition. The 

 artificial basins, arranged in the form of cascades and capable of 

 communication amongst themselves, receive the waters coming 

 from a higher level; the latter become charged with boracic 

 acid, and at the end of twenty-four or thirty-six hours they are 

 conducted into evaporating caldrons and replaced by fresh sup- 

 plies of cold water. 



* Translated fropa the Compies Rendus, August 23, 1858, p. 317. 



