ON THE BORACIC ACID OE CENTRAL ITALY. 295 



in the centre. Forcing its way through the fissures by its specific gra- 

 vity, the water comes in contact with the highly-heated gases and rocks, 

 and is immediately converted into steam, which, from its elasticity and 

 enormous increase in volume, is ejected with great force, hut is con- 

 densed as soon as it reaches the surface of the basin by the colder water 

 around. This incessant vaporization of the water and its subsequent 

 liquefaction produce a great commotion in the lagoon, a turbulent little 

 fountain rising to the height of a foot, and causing a succession of con- 

 centric ripples. All this time there is a copious discharge of sulphur- 

 etted hydrogen, which in one case I distinctly perceived at night-time 

 full a quarter of a mile from a lagoon, and before I knew of its existence 

 there. 



Having remained twenty-four hours subject to continual agitation, 

 the water, which has assumed a slate-blue colour, is let out of the lagoon 

 and passes into a canal, through which it is conducted into a second 

 basin at a lower level ; thence it passes through several more, of similar 

 construction, each lower than the preceding one. In this manner the 

 water dissolves the boracic acid in the fissures, and brings it up mechani- 

 cally mixed with it. No other object appears to be attained by making 

 all the water pass through the chain of lagoni than to obtain boracic 

 acid of uniform density, though Dumas expressed to Count Lardarel the 

 opinion that probably, by some ingenious device, it might be brought 

 to a saturation of 15 to 16 per cent. — a great desideratum. The tempera- 

 ture of the liquid is considerably above 212° Fahr., and dense vapours 

 rise for many yards above the ground, heating the air so much as to 

 render it unpleasant to remain long near them. Efflorescent minerals and 

 decomposed rock, ejected with the steam, lie scattered all round on the 

 heated surface of the ground, along with sulphur incrustations and 

 many sulphates, such as gypsum, alum, and sulphate of ammonia, be- 

 sides iron pyrites in minute veins in the fragments of rocks. 



The water passes at stated intervals, while still boiling, into 

 the VascOj a tank sixty feet square, covered by a tiled roof sup- 

 ported at the sides by slight brick pillars. Here the greater part of the 

 mechanical impurities, clay, and the more insoluble sulphates, sink to 

 the bottom, and the water regains its limpidity. The next operation i3 

 to concentrate the solution of acid, which is effected in the adjoining 

 building containing the evaporating pans : these are so exceedingly inge- 

 nious and simple as to merit particular consideration ; Count Lardarel, who 

 invented them, has given them the name of Adrian evaporators. Three 

 parallel series of shallow leaden divisions, called Scanelli, are placed in a 

 line, each being a third of an inch lower than the one before it, from which 

 it is only separated by a leaden partition half an inch broad, and as deep- 

 The scanelli are placed transversely, and are six feet long by twenty-two 

 inches wide ; they are arranged under a roof, to keep off the rain, but the 

 evaporation is not in any way impeded, since the sides are open, and only 



