2 j4 ■^^- Delaval on the Caufe of the 



aqueous meteors. It is certain that fome of 

 the moft extenfive, and permanent vapours, 

 which have been obferved in the atmofphere, 

 were not formed of aqueous or humid matter. 



The mift, which obfcured the air, during 

 the fummer of the year 1783, was remarkable 

 for its extent. For, it involved almoft all 

 Europe, a part of Afia, and of Africa, and per- 

 haps reached much further : its altitude was 

 fo great, that the Alps were immerfed in it. 



In moft parts of Europe, the air, during the 

 prevalence of this vapour, was unufually dry. 

 For, the hydrometer did not rife to the point 

 which denotes moifture: fait cryftallized ii) 

 . brine pits, before the ordinary period ; and 

 other procefTes, which depend upon evaporation, 

 were accelerated. ' 



Several other curious obfervations, relative 

 to this fubjecV, are contained in an account 

 written by M. Senebier of Geneva.* 



When the air is replenifhed with very denfe 

 vapours, it tranfmits only the lefs refrangible 

 rays, from whole mixture an orange, or red, 

 colour is produced. Diftant mountains covered 

 with fnow, clouds, or other white fubftances, 



♦ The paper of this excellent philofopher is Inferted in 



tbe Journal of the Abbe Rozier (Anno. 1784. May.) The 



fame coUeflion contains alfo inftruftive accounts of that 



fubjeft by M. Toaldo, ProfeiTor at Padua, M. Lamanon, 



, {^ad M. Marcorelle, Baron d'£fcalle, (Jan. 1784.) 



' which 



