296 ON THE BORACIG ACID OF CENTRAL ITALY. 



a few brick pillars of the lightest construction are employed to support 

 the roof. The length of the building is often several hundred feet. At 

 the commencement of the operation a man turns a tap, which lets the 

 water flow in regulated quantities from the vasco into the first scanello, 

 everything depending on this precaution ; it now flows on from one divi- 

 sion of these diaphragm pans to another, until, arriving at the end of 

 the building, it passes along the second row of divisions, and finally back 

 through the last series into the diagonal corner, where there is a large and 

 deep reservoir called the Caldaja a sale. In its progress the water gra- 

 dually evaporates. As I mentioned before, when it entered the building, 

 it only contained 1 J or 2 per cent, of boracic acid, but after having passed 

 through fifty or sixty divisions, it assumes a decidedly yellow tinge, in- 

 creasing in intensity until finally it becomes a bright golden yellow fluid, 

 having a characteristic odour. The internal arrangements of the evapo- 

 rators, though they may appear simple enough, were the result of much 

 thought. The leaden pans are supported by beams over a low vaulted 

 .-team-passage, lined with hydraulic cement, to protect the stone-work 

 aud keep in the heat. For this purpose a sojfione is vaulted over with a 

 stone dome, about ten feet high, firmly bound with wrought-iron bars 

 water is admitted, and the imprisoned high-pressure steam thereby pro- 

 duced acquires immense power, and thumping loudly against the dome, 

 the jets - of water seem ready at every moment to undermine the struc- 

 ture. The steam passes thence through the vaulted passage into the lower 

 chamber of the evaporators, and, having traversed it from end to end, 

 finds its way out into the open air through a chimney at the opposite end. 

 What formerly took 62 hours to evaporate, is periormed by this beautiful 

 contrivance in 12, the expense being also proportionately diminished. 



From the caldaja a sale the syrupy liquor is periodically conducted 

 along a wooden jfipe to the Bollajo, or crystallizing house, in which a 

 series of large barrels, 3 or 3^ feet in diameter, are ranged in a line. 

 When it is desired to fill them, all that is necessary to be done is to re- 

 move a plug placed over the centre of each barrel in the pipe which runs 

 round the building : the liquor remains four days in the barrels, during 

 which time it has crystallized at the sides and bottom to the thickness 

 of several inches, the liquid portion is then withdrawn by removing a 

 plug, and finds its way along a longitudinal drain, by which means it is 

 all saved for future use. No one could fail to adrnire these beautiful 

 processes, whose characteristic merit is that they do not necessitate 

 anything being lost. 



The boracic acid crystallizes in hexagonal plates, about the size and 

 thickness of a wafer, having a waxy appearance and pearly lustre. From 

 their peculiar form they naturally retain much water mechanically 

 mixed, so that they are first put in large wicker baskets, Corbelli, to 

 drain, and then emptied out on the floor of a large airy chamber, called 

 the Asciugatojo, or drying house. The brick floor is heated, like the 



