Quetelet on the Electricity of the Air. 



409 



there. In the lower stratum absolute dryness does not exist. 

 It is more or less moist, constantly disturbed, and traversed, 

 although with considerable difficulty, by the positive electricity 

 which can at times unite with the opposite electricity of the 

 earth ; but these never exist in intimate connection. The 

 action is like that of two conductors charged with opposite 

 electricities and placed at a distance : " the opposite fluids tend 

 to unite through the more or less moist air that is interposed, 

 but their charges remain the same. If the losses are constantly 

 renewed, the positive fluid of the upper layer gives rise to all 

 the electrical phenomena that we observe upon our globe. 



Being partially retained by the dryness and relative immo- 

 bility of the stratum in which it finds itself, it operates through 

 the lower stratum, which is always agitated and always more 

 or less humid, and partially paralyzes the electricity indicated 

 by our instruments on the surface of the globe." 



In our northern hemisphere, the electricity is stronger in 

 winter than in summer. The layer of the atmosphere that is 

 constantly disturbed is not so thick at this season, and thus we 

 are closer to the upper layer. In the course of a year, this 

 augmentation of electricity and diminution of height becomes 

 very apparent ; between June and January, or December, the 

 variation is as much as 1 to 10. Nor is the diurnal variation 

 less noticeable, " the electricity becomes stronger towards the 

 approach of night, and its minimum occurs a little after the 

 hours of strongest heat during the day. It is towards three 

 o' clock p.m. in the summer time, that the electrified layer which 

 acts upon our instruments appears to be furthest removed from 

 the earth." It should also be remembered that as heat aug- 

 ments, and the air becomes drier, its conducting j)ower is 

 diminished. During the night the solar action is insensible, 

 and the variation is much less, and that which occurs appears 

 to be the result of changes in the opposite atmosphere. 



M. Quetelet observes that we have no precise ideas of the 

 absolute force of electricity, and that we do not know whether 



vol. n. — NO. VI. P F 



