364 SCIENCE PROGRESS. 



has been ascertained to have fallen from the cloud near- 

 Sienna, is evidently freshly vitrified, and is black, having 

 every sign of having passed through an extreme heat ; when 

 broken, the inside is of a light grey colour mixed with 

 black spots, and some shining particles, which the learned 

 here have decided to be pyrites, and therefore it cannot be 

 a lava, or they would have been decomposed. Stones of 

 the same nature, at least as far as the eye can judge of 

 them, are frequently found on Mount Vesuvius ; and when 

 I was on the mountain lately, I searched for such stones 

 near the new mouths, but as the soil round them has been 

 covered with a thick bed of fine ashes, whatever was thrown 

 up during the force of the eruption lies buried under those 

 ashes. Should we find similar stones with the same vitri- 

 fied coat on them on Mount Vesuvius, as I told Lord 

 Bristol in my answer to his letter, the question would be 

 decided in favour of Vesuvius ; unless it could be proved 

 that there had been, about the time of the fall of these: 

 stones in the Sanese territory, some nearer opening of the 

 earth, attended with an emission of volcanic matter, which 

 might very well be, as the mountain of Radicofani, within 

 fifty miles of Sienna, is certainly volcanic. I mentioned to 

 his lordship another idea that struck me. As we have 

 proofs during the late eruption of a quantity of ashes of 

 Vesuvius having been carried to a greater distance than 

 where the stones fell in the Sanese territory, and mixing 

 with a stormy cloud have been collected together just as 

 hailstones are sometimes into lumps of ice, in which shape 

 they fall, and might not the exterior vitrification of those 

 lumps of accumulated and hardened volcanic matter have 

 been occasioned by the action of the electric fluid on them ? 

 The celebrated Father Ambrogio Soldoni, professor of 

 mathematics in the university of Sienna, is printing there a 

 dissertation upon this extraordinary phenomenon, wherein, 

 as I have been assured, he has decided that those stones were 

 generated in the air, independently of volcanic assistance." 



Soldoni's account contains the following additional de- 

 tails : "Two ladies being at Coyone, about twenty miles 

 from Sienna, saw a number of stones fall with a great noise: 



