SCIENTIFIC NEWS. 221 



«« of the Siennefe territory ; they fell about eighteen hours 

 €t after the enormous eruption of Mount Vefuvius : which 

 «' circumftance leaves a choice of difficulties in the folution 

 " of this extraordinary phenomenon. Either thefe ftones 

 " have been generated in this igneous mafs of clouds, which 

 «* produced fuch unufual thunder ; or, which is equally incre- 

 " dible, they were thrown from Vefuvius, at a diftance of at 

 •' leaft 250 miles; judge then of its parabola. The philofo- 

 " phers here incline to the firft folution. I with much, Sir, 

 " to know your fentiments. My firfl objection was to the 

 " fa6t itfelf ; but of this there are fo many eye witnefles, it 

 " feems impoffible to withftand their evidence." (Phil. Trans. 

 for 1795. p. 103.) Sir William Hamilton, it feems, alio 

 received a piece of one of the largeft ftones, which weighed Weight, 

 upwards of five pounds ; and had feen another, which weighed 

 about one. He likewife obferved, that the ouitfide of every 

 ftone which had been found, and had been afcertained to have 

 fallen from the clouds near Sienna, was evidently frefhly 

 vitrified, and was black, having every fign of having pafled 

 through an extreme heat; the infide was of a light grey 

 colour, mixed with black fpots and fome finning particles, 

 which the learned there had decided to be pyrites. 

 (To be continued.) 



SCIENTIFIC NEWS, &V. 



Dimenfions and Nature of the New Planets Ceres and Pallas. 

 By Dr. Herschel. 



Dr. HERSCHEL's obfervations on the two lately dif- 



covered celeftial bodies were read before the Royal Society, 



6th of May. 



Dr. Herfchel begins with ftating the refult of his attempts Obfervation of r 



r it r i n it i i ™ K the diameters of 



to mealure the diameter or the ltars dilcovered by Piazzi and Ceres and Pallas. 



Olbers. He employed the lucid difc micrometer, which con" 



lifts of an illuminated circle viewed with one eye, while the 



other compares with it the magnified image formed by the te- 



lefcope; and he concludes, that the apparent diameter of 



Ceres was 22", and of Pallas 17'' or 13", at the diftance of 



nearly 1.634, and 1.187 from the earth refpeclively, whence 



the apparent diameters at the diftance of the earth from the 



fun would be .35" and .2 1'' or . 16" refpe&ively, and that their 



-real 



