300 LIGHTNING AND RAIN. 



moisture, and thus prevented from being col- 

 lected in a Leyden battery. It is accumulated in 

 transparent aqueous vapour, as I shall proceed to 

 shew by the most decisive facts, and by the ex- 

 periments of different philosophers, from which 

 it darts through the neighbouring clouds in such 

 a manner as to present the appearance of pro- 

 ceeding from them ; while it is an optical illusion 

 that may be corrected by a philosophical exami- 

 nation, in short, that a large body of transpa- 

 rent elastic vapour from the tropics, may be 

 compared to an immense Leyden battery, filled 

 with an igneous fluid which is discharged in the 

 concentrated form of lightning on approaching 

 mountains or currents of cold air. 



When the inquiry is divested of all extraneous 

 and hypothetical considerations, it may be re- 

 duced to the following conditions. 



If it can be shewn, that transparent elastic va- 

 pour is the vehicle of atmospheric electricity, and 

 that it is rapidly condensed during discharges of 

 lightning, it will necessarily follow, that the 

 caloric of such vapour is given out in the con- 

 centrated form of electricity during a thunder 

 storm. 



In reply to this reasoning it may be objected, 

 that heavy rains are often unattended with 

 lightning. To which I answer without fear of 

 contradiction, that the formation of clouds and 

 precipitation of rain are far more rapid during 

 thunder storms than when there is no lightning. 



