ATMOSPHERIC ELECTRICITY. 13£ 



•ity commonly increases. The electricity never becomes nega- 

 tive in either of the above cases. 



Father Beccaria, in his experiments on the electrified air of a The artificial 



room, found that the electricity is proportional to, and there- electricity in a 

 r .11 .«'••■ a J. i • room is pro- 



fore most probably resides in the vapours floating therein. port ioncd to 



The same conclusion may, therefore, as he observes, be natu- its moisture. 



rally applied to the atmospherical electricity, which is not suf- ' 



ficient in general to produce electric figures, in electrometors 



which are not insulate!. The two last propositions, 8 and 



9, relate to such phenomena as take place when the weather 



either becomes overcast or clears up. The following relates to 



the effects of vapour or moisture, as shewn by the hygrometer. 



10. In the morning, if the hygrometer indicates a great de- in very dry 



gree of dryness, very little difference from that of the preceding mornnigs^elec- 



day, then even before sun -rise an electricity takes place, caus- shewn; but if 



ing junction, adhesion, or divergence, of the ball: and its tn e air be not 



very dry the 

 intensity is greater the drier the air, and the less that dryness electricity ap- 



differs from that of the preceding day. But if no suclr great pears after sun 

 dryness obtains, no perceptible electricity takes place, till sun- 

 rise, or a short time after. 



11. The electricity of the air gradually increases as the sun The electricity- 

 rises higher. The gradual increase begins sooner, according as ureases as the 



. „ . . ,. ... sun rises high- 



the hygrometer continues after sun-n«e to indicate a higher er> & c> 



degree of dryness, and as such dryness more speedily increases. 

 This increase, both of intensity and speedy recovery, when taken 

 off, last in serene days, when the wind is net violent, till the 

 sun draws near its setting, provided the hygrometer keeps near 

 the highest degree it has reached. But when the sun is near 

 setting, and in proportion as the hygrometer retreats, the inten- 

 sity of the daily electricity is diminished, at the same time that . . 

 the quickness with which it is revived in the apparatus, when 

 taken off, becomes greater. 



12. Though the hygrometer may indicate equal degrees of Difference 

 dryness in the middle of the day, on different days, yet the t ^^ n ? ^ n h °eat* 

 time in which the apparatus recovers its electricity on those are diffemt. 

 days is less, the greater the increase of heat j and when the heat 



is greater, the electricity arises later in the morning, and fails 

 sooner in the evening 



13. The friction of winds against the surface of the earth is Winds do not 

 not the cause of atmospheric electricity. Impetuous winds dimi- fricityby fric" 



JK. 2 , nishtion. 



