METEOROLOGY. 



METEOROLOGY. 



Constituent parts of the Atmosphere Evaporation Rain Fog or Mist Dew 

 Snow Hail Coronse, or Haloes Parhelia, or Mock-suns Fiery Meteors 

 Aeroliths Aurora Borealis Ignis Fatuus, or Jack with a Lantern Wind 

 Meteorological Instruments, &c. 



METEOROLOGY is that part of Natural Philosophy which 

 explains the various phenomena of the atmosphere, as 

 the clouds, rain, hail, dew, &c. 



The Atmosphere is a vast body of air surrounding the 

 earth, and extending to about 45 miles above its surface. 

 It has been found when decomposed, as was observed 

 under the article Pneumatics, to consist of two gases, 

 oxygen and azote, containing at the same time about 

 one part in seventy of Aqueous Vapour independent ot 

 other substances. One cubic foot of air near the sarface 

 of the earth is found to weigh about one ounce and a quarter, 

 being about 800 times lighter than water. 



A certain process called Evaporation is continually 

 going on, which supplies the air with aqueous vapour, 

 ultimately to form rain, dew, &c. It is calculated that 

 five thousand millions of tuns of water are carried off 

 from the Mediterranean Sea alone in a summer's day, and 

 that twenty millions of tuns are carried off the Thames 

 in the same time ; also that one hundred thousand cubic 

 miles of water are by this process annually taken up by 

 the atmosphere, the greatest part of which, when it has 

 arrived at a certain height, being condensed into clouds. 



As it is through the agency of caloric that water be- 

 comes suspended in the air, it is natural to expect that 

 when the caloric is by any means abstracted, a conden- 

 sation will take place, and that the aqueous particles 

 will form drops. Something more than the mere parting 

 with the caloric, is now thought necessary for the pro- 

 duction of rain ; and as it is known that electricity is 

 carried off the earth by evaporation, it is generally un- 

 derstood that rain is in great measure an electrical phe- 

 nomenon ; so that when the clouds part with their elec- 

 tricity, which they may do in various ways, the result is 

 a conversion of the aqueous vapour into drops of water, 



