l66 PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



cretaceous grey water, which, after evaporating and filtrating away, left every 

 place covered with it to the height of 1 or 3 lines; and all the iron-work that 

 was touched by it became rusty. The shower extended from n. \ n. e. to s. -J- 

 s. w. over the fields, about 70 miles in a right line from the vertex of Etna. 

 There is nothing new in volcanos having thrown up sand, and also stones, by the 

 violent expansive force generated within them, which sand has been carried by 

 the wind to distant regions. But the colour and subtilty of the matter occasioned 

 doubts concerning its origin ; which increased from the remarkable circumstance 

 of the water in which it came incorporated; for which reasons some other prin- 

 ciple or origin was suspected. 



It became therefore necessary by all means to ascertain the nature of this 

 matter, in order to be convinced of its origin, and of the effects it might pro- 

 duce. This could not be done without the help of a chemical analysis. To do 

 this then with certainty, I endeavoured to collect this rain from places where it 

 was most probable no heterogeneous matter would be mixed with it. I therefore 

 chose the plant called Brassica Capitata, which having large and turned up leaves, 

 they contained enough of this coloured water; many of these I emptied into a 

 vessel, and left the contents to settle till the water became clear. This being 

 separated into another vessel, I tried it with vegetable alkaline liquors and mineral 

 acids; but could observe no decomposition by either. I then evaporated the 

 water, to reunite the substances that might be in solution: and touching it again 

 with the aforesaid liquors, it showed a slight effervescence with the acids. When 

 tried with the syrup of violets, this became a pale green ; so that I was persuaded 

 it contained a calcareous salt. With the decoction of galls no precipitation was 

 produced. The matter being afterwards dried in the shade, it appeared a very 

 subtile, fine earth, of a cretaceous colour, but inert, from having been diluted 

 by the rain. 



I next thought of calcining it with a slow fire, and it assumed the colour of 

 a brick. A portion of this being put into a crucible, I applied to it a stronger 

 heat, by which it lost almost all its acquired colour. Again, I exposed a portion 

 of this for a longer time to a very violent heat, from which a vitrification might 

 be expected; it remained however quite soft, and was easily bruised, but returned 

 to its original dusky colour. From the most accurate observations of the smoke 

 frum the 3 calcinations, I could not discover either colour or smell that indicated 

 any arsenical or sulphureous mixture. Having therefore calcined this matter in 

 3 portions, with 3 different degrees of fire, I presented a good magnet to eacl ; 

 it did not act either on the first or second; a slight attraction was visible in many 

 places on the third; this persuaded me, that this earth contains a martial prin- 

 ciple in a metallic form, and not in a vitriolic substance. 



The nature of these substances then being discovered, their volcanic origin 



