VOL. LXXII.] PHILOSOPHICAL TRANSACTIONS. it)/ 



appears; for iron, the more it is exposed to violent calcination, the more it is 

 divided, by the loss of its phlogistic principle; which cannot naturally happen 

 but in the great chimney of a volcano. Calcareous salt, being a marine salt 

 combined with a calcareous substance by means of violent heat, cannot be other- 

 wise composed than in a volcano. As to their dreaded effects on animals and 

 vegetables, every one knows the advantageous use, in medicine, both of the one 

 and the other, and this in the same form as they are thus prepared in the great 

 laboratory of nature. Vegetables, even in flower, do not appear in the least 

 macerated, which has formerly happened from only showers of sand. 



How this volcanic production came to be mixed with water may be conceived 

 in various ways. Etna, about its middle regions, is generally surrounded with 

 clouds that do not always rise above its summit, which is 2900 paces above the 

 level of the sea. This matter being thrown out, and descending on the clouds 

 below it, may happen to mix and fall in rain with them in the usual way. It 

 may also be conjectured, that the thick smoke which the volcanic matter con- 

 tained might, by its rarefaction, be carried in the atmosphere by the winds, over 

 that tract of country; and then, cooling so as to condense and become specifi- 

 cally heavier than the air, might descend in that coloured rain. I must, how- 

 ever, leave to philosophers, to whom the knowledge of natural agents belongs, 

 the examination and explanation of such phenomena, confining myself to obser- 

 vation and chemical experiments. 



p. s. On Friday the 4th of May, about a quarter past 3 in the afternoon, a 

 slight shock of an earthquake was felt in the country about Etna, which became 

 more sensible at some distance from the mountain; its direction was from north 

 to south. The volcano had continued its flames and explosions; and the night 

 before, a column of smoke, composed of globes as it were piled on each other, 

 had ascended over the crater to double the height of the mountain, as far at least 

 as one could judge at the distance of 22 miles, which the vertex is in a right line 

 from this city. This remained the whole night perpendicular, only one of the 

 globes had separated and lengthened out to the westward from the summit. Now 

 and then all the inside of the column, and of the lengthened outpart, became 

 illuminated by electric tire, which was of a deep red colour, and gradually went 

 out again, beginning at the bottom, in about *2 seconds. The fire has continued 

 on the crater till this day, May 8th, ejecting red-hot masses or stones, which 

 rolling beautifully down the cone, have illuminated this region; some lava has 

 run over from the crater towards the w. n. w. but without having force enough 

 to burst the sides or walls of the volcano. 



