232 ANNUAL OF SCIENTIFIC DISCOVERY. 



of Vulcano, which is situated about twelve miles north of Sicily have enabled 

 me to make a few experiments, winch, though not so complete as I could 

 have wished, appear to throw some light upon this point. " The height of 

 the volcanic mountain is estimated at about 2,000 feet, and its crater is about 

 700 feet deep. The area at the bottom, which may be about ten acres in ex- 

 tent, is covered with small, loose pieces of limestone, just as though it had 

 been Macadamized, and the ground is so hot as rapidly to destroy the leather 

 of the shoes. On thrusting a thermometer between the stones, it indicated, at 

 different points, temperatures varying from 250 to 500 Fahrenheit. On looking 

 over this area from the top of the crater, one side of it appeared as if covered 

 over with beautifully- white drifted snow. On reaching the spot, however, this 

 white appearance was found to be caused by a deposit of finely-crystallized 

 boracic acid. On removing this incrustation, which formed a layer of about 

 an inch in thickness, and digging with a pick-ax, there spumed up a mass of 

 red-hot fused lava, similar in appearance to the slag of a glass-house ; this 

 consists of fused salirs matters in cohesion with volcanic debris. In other 

 parts of the crater there are holes like foxes' holes, from which blue jets of 

 volcanic flame *yQ issuing continually, and a deposition of sulphur occurs all 

 around. 



" The boracic acid rises in vapor, and condenses on the surface of the ground 

 at the bottom of the crater like a light drifted snow ; and when gathered up, 

 the surface becomes covered again with sublimed acid in two or three days. 

 To Ascertain this point more decidedly, some hogshead casks, having their 

 heads removed, were filled with broom-plants and twigs, and were placed over 

 Varts of the area from which the boracic acid had been carefully cleared away, 

 tn a few days the acid had been vaporized into them, and had deposited in 

 n-ystals like hoar-frost all over the twigs. On digging down for about eight 

 nches, wherever this boracic acid occurs on the surface, a red-hot mass of sal- 

 ammoniac is always found ; sulphur comes up also with these. This volcano 

 is said to realize to the proprietors about 1,000 per annum. The products 

 are sulphur, from fusing the stone ; sal-ammoniac, from the lixiviation of the 

 scoria or lava ; and boracic acid, large quantities of which are reported to be 

 obtained annually from this source. The sides of the volcano are of sulphur- 

 stone, and brimstone is dug up all around for miles. The mountains produce 

 also alum, which exists in the schistose rocks ; and there are likewise large 

 beds of lignite ; but nowhere do we find sal-ammoniac or borncic acid, either 

 at Vulcano or in Tuscany, separate from one another. Had they done so, we 

 should certainly have found traces of it somewhere, but, so far as I know, this 

 has never been observed ; and it is certain that, at Vulcano, whenever the 

 acid lying on the surface is removed, the melted matter underneath is found 

 to contain salts of ammonia. It follows, therefore, that they must both be 

 produced from one and the same stratum, in which they occur in some form 

 of combination, from which they are separated by heat. In what substance 

 can the}^ exist together ?" 



An examination of the sublimate scraped from the surface of the crater, 

 shows that the ammoniacal salt was not a portion of the fused mass mentioned, 

 but had been obtained by its lixiviation and subsequent crystallization. The 



