492! 



DOMAIN XII. VOLCANIC. 



earthy matters which predominate are argil and 

 silex. 



" Ifc mi bt be imagined that the phenomena 

 of this eruption, and especially those which took 

 place from the evening of the 15th to the 20th, 

 would have a considerable influence on the at- 

 mosphere of Naples, yet the meteorological ob- 

 servations, communicated to me by the astrono- 

 mer Casselli, prove that the barometer had ex- 

 perienced no material alteration. Casselli made 

 Barometer, use of an English barometer, divided into inches 

 and hundredth parts. From the llth of June 

 to the 15th it maintained itself between 29,51 

 and 29,68. On the 16th and 17th it was sta- 

 tionary at 29,60. The 18th it varied from 29,55 

 to 29,52. The 1 9th from 29,50 it rose to 29,51. 

 The 20th it stood at 29,46. The 21st between 

 29>,46 and 29,49- I conversed on this subject 

 one day with Cotte, tolerably well known by his 

 meteorological observations, who considered it 

 as a very extraordinary circumstance. We were 

 at the time at the house of Lametherie, who 

 showed me a memoir on this subject written by 

 M. de Buch, a learned mineralogist of Prussia, 

 inserted in the Journal de Physique of Thermi- 

 dor, An 7> under the title of Considerations sur 

 le barometre, in which I found the following 



Buch's ... . _ 7 



account, passage, which to me seemed curious : c Vesu- 



