132 ATMOSPHERIC ELECTRICITY. 



nish the intensity of the electricity of clear weather. And if 

 . they be damp they diminish its intensity, by rendering the insula- 

 tion both of the atmosphere and of the apparatus more imperfect. 

 Other factsand Father Beccai ia made many experiments to discover whether 



observations , • ', . J r . . 



on the friction tlie fnctionof air against conducting bodies produced electricity. 



of winds. He used the bellows, and also turned fans of gilt pasteboard 



very swiftly round on an insulated axis, but obtained no elec- 

 tricity either in damp or dry weather. He had before observed, 

 . that air produces electric signs, when it strikes their glass*. Ha 

 found also that the umbrella, with an insulating handle, which 

 the French call paratonneres, never exhibited the least electri- 

 city when held obliquely to the wind. To these I may add, 

 that the very sensible electrometer, of Bennet, cioes not become 

 electrified by blowing pure air upon itf. The proposition of 

 Beccaria does not, however, rest upon electrical experiment, 

 but is likewise supported by a variety of actual observations on 

 the state of the atmosphere. And though these cannot be 

 transcribed, on account of their length, yet I am unwilling to 

 pass over in silence his very cogent remark, that if the elec- 

 tricity in any degree arose from the friction of winds against 

 the ground, it would be found the greatest near the surface of 

 the earth, but the contrary is the fact. 



Night elec- XIV. In cold weather, if the sky be clear, the wind not 



tncity m cold v i i entj and the air considerably dry, an electricity of consider- 

 able intensity arises after sunset, as soon as the dew begins to 

 fall. The quickness with which the apparatus recovers its 

 electricity after being touched, is greater than during the diurnal 

 electricity, and it disappears very slowly. 



and also in XV. In temperate or warm weather, and in the same cir- 



temperateor cumstances of wind and moisture, an electricity perfectly 

 warm weather. . , 



similar to the above takes place as soon as the sun has set ; 



but its intensity is not so constant, it begins with more quick- 

 ness, rises to a state of more speedily recovering its intensity 

 after being touched, and ends sooner. 

 Moisture af- XVI. When the air in the above circumstances, is less dry, 

 fectsthe insu- the electricity is less intense, by reason of the insulation being 

 rendered more imperfect, but its quickness in recovering its 



* Seep. 363, vol. I. on Artificial Electricity. § 776. 

 t Ph. Tram. rol. JLXXVII. p, SO, 



intensify 



