STATE HORTICULTURAL SOCIETY. 45 



to be, is that there has been no complete transition of such fog or haze 

 from the negative to the positive state. 



If the theory advanced be correct that high and low atmospheric 

 pressures are electric phenomena, then il follows that the currents of air 

 to which they give rise are electric jjhenomena also. Time and the oc- 

 casion prevents me from going into details to establish these propositions. 

 There are however some observations made by Or. Wislizenus of St. 

 Louis which are pertinent here. lie says, — in his remarks on his tables 

 on electric observations published in the Missouri Statistical Report for 

 1867, — that from 1861 to 1867, he had observed the atmosphere to be 

 eleven thousand two hundred and thirteen times in a positive state ; four 

 hundred and forty times in a negative state ; and three thousand four 

 hundred and seventy-six times neutral, that is the electricities in equi- 

 librium 



I have already stated that the Earth is always negative, while the 

 charge on the upper atmosphere is always positive. As the electrometer 

 of Dr. Wislizenus is insulated and placed some thirty-five or forty feet 

 above the surface of the Earth, it can only show a negative state when 

 an electric Avave is rolling over, and streams of negatively electrified 

 vapor are flowing upwards. He tacitly admits this, when he says that 

 "instantly with the approach of a storm the negative makes its appear- 

 ance, and of such high tension that the electrometer cannot measure 

 it." When however the rain sets in, the negative tension decreases until 

 it becomes zero, or when the atmosphere becomes positive. Why .' Be- 

 cause the rain is positively electrified and neutralizes the negative charge 

 on the surface of the Earth. 



He adds "of the four hundred and forty times that the atmosphere 

 was observed to be charged with negative electricity, it was found one 

 hundred and sixty times to be connected with thunder-storms: one hun- 

 dred and fifty-eight times with rain only ; one hundred and three times 

 with dry storms, that is, without rain, or thunder and lightning, and 

 seventeen times with snow. The dry storms, no doubt, were the effect 

 of a rolling electric wave, whose storm-center, where precipitation took 

 place, passed north or south of the observer. 



He also says, ." Snow is generally accompanied with positive elec- 

 tricity, and fogs, always." Why.' Because snow receives a positive 

 charge in the upper region of the atmosphere, and in descending neu- 

 tralizes and finally changes to the positive the surface stratum of atmos- 

 phere. In the (ase of fogs and in that of dew, the positive condition to 

 which the atmosphere is changed is owing to the same cause operating 

 as in rain and snow, with this difference ; rain and snow descend through 

 the atmosphere by their own specific gravity; while dew and fog are 

 vapors having greater levity than the atmosphere; when they become 

 positively charged, they are precipitated ag^ainst their specific gravity by 

 the law of electric discharges between ojjposite poles. 



We have spoken of areas of low barometric pressure and of winds 

 blowing toward them ; and of areas of high barometric pressure and of 



