324 Intelligence and Miscellaneous Articles. 



served by M. Matteucci, of which the experiment just described is 

 a faithful representation. 



When I produced a series of discharges, by bringing the positive 

 plate too near the negative sphere below, I saw the needle of the 

 galvanometer deflect, sometimes in one, and sometimes in the other 

 direction, making very irregular movements, instead of preserving 

 the constant deviation which it experienced when there was no dis- 

 charge. This is another faithful representation of what takes place 

 in nature — M. Matteucci having observed that during storms the 

 oscillations of the needle of the galvanometer are sudden and fre- 

 quent, while on calm and clear days (the only ones on which the 

 normal phenomenon could be observed) the deflection of the needle 

 remains almost constant. 



I do not dwell upon the other phenomena of the same kind 

 observed by M. Matteucci, such as the presence of very feeble and 

 variable currents in a wire terminating in two points of the surface 

 of the earth situate on the same parallel and on the same level ; 

 points whose electrical condition should obviously be the same, or 

 only slightly differ in either direction, owing to accidental circum- 

 stances. The slight currents from south to north, again, which M. 

 Matteucci has observed in wires placed horizontally in the direction 

 of the meridian, and having their ends constantly in the ground, 

 are probably due to the fact that the negative tension of the earth, 

 other things being the same, gradually increases from the equator to 

 the poles, where it is a maximum. This increase is a necessary 

 consequence of the influence which should be exerted on the negative 

 electricity of the earth by the great quantity of positive electricity 

 accumulated in the atmosphere near the poles, owing to the trade- 

 winds. The discharges which take place between the contrary 

 electricities in the polar regions where they are accumulated, give 

 rise, as I have shown, to the polar auroras and the electrical currents 

 which accompany them — currents more powerful than those of 

 which we have spoken, and which differ from them both in intensity 

 and in direction. 



The electrical phenomena which occur at the surface of our 

 globe and in our atmosphere are sufficiently complex. There is first 

 of all a general fact — that is, the accumulation, owing to the trade- 

 winds, in the atmosphere of the poles of positive electricity, with 

 which the air of the equatorial regions is constantly charged by the 

 particles of aqueous vapour which rise from the seas. The influ- 

 ence of this electricity accumulates and condenses near the poles a 

 great proportion of the negative electricity which the solid part of 

 the globe possesses, at the same time that it in turn is condensed. 

 The more or less frequent discharges that take place between the 

 condensed electricities through the atmosphere, give rise to the polar 

 auroras, whose appearance is always accompanied by electrical 

 currents circulating in the ground ; these currents show themselves 

 either by their action on compass-needles, or by their transmission 

 through telegraph-wires. 



But, besides the general and dominant fact which we have men- 



