ATMOSPHERIC ELECTRICITY. 297 



Mr. Erman prot ured a tube of glafs 14 feet long, which he A fixed rod not 

 Covered vvi'h varntfh, and through which he introduced a j cs Vituationwith 

 metallic wire which pa (Ted above the upper part, and had regard to the 

 the electrometer adapted to its lower extremity. A froal'chMjred!"* 

 piece of amber being rubbed and applied to the upper end 

 of the wire, produced a divergence in the leaves. The 

 electricity of the air had not, however, any influence on this 

 fixed, and very nicely infulated point ; which (hews, that the 

 air furrounding a point is more adapted to deprive it of elec- 

 tricity than to communicate it. Another ele&rometer which 

 was raifec! from the earth at the fa.;ie time produced a great 

 divergence. 



Mr. Erman wiflhed to know whether two bodies in the fame Two electrome- 



atmofpheric ftratum reciprocally modify their electric ftate, ters br ° ught j nt0 



1 . . . , contaft, and 



when their diftance is altered in either direction. Two gold then horizontally 



leaf electrometers equally feniible, and armed with rods three fe P 3rated affe & 

 r , r , . . .,,,... . . , eacn other ac- 



Jeet long, one of which was bended, 10 that its point could cording to the 



be placed near that of the other electrometer, on the fame laws of bodies 

 horizontal line were held at arms length from each other, and t iified. 

 touched with the finger to difcharge, and put them in equili- 

 brium with the furrounding air. They were afterwards brought 

 towards each other horizontally, an ! when they were fuf- 

 ficiently near to permit their atmofpheres to a6t on each other, 

 there was a divergence of main.? electricity on both fides, 

 which came to its maximum when the electrometers were in 

 contact. They were again (eparated, and the divergence 

 difappeared, both being at the ftate of Zero. One of the 

 wires of thefe electrometers was put in comae! with the 

 earth, when the divergence of the other infulated electrometer 

 (uddenly diminifhed to half its former quantity ; a fact that 

 alfo proves that the whole depends upon the elediuiiy in- 

 herent in bodies, and not at all upon that of Lire a.m fohere. 



When the electrometers were removed froftn ea h Otherj Continuation of 

 that which was touched with the finger indicated ,lus in a the experiment, 

 degree equal to the mvms A had before (he is •.<. It me two 

 elect -ometers be touched with the finger, no further -n>- 

 peaiance of the minus divergence is ieen in eillu. of them; 

 but if they be then (eparated both will exhibit />/«„ C.~n 

 thefe phenomena be attributed to the air? or is k poffible to 

 avoid admitting in thefe experiments the influence of electric 

 a'moipheres, and the law of the condenfer? — It is, therefore, 



well 



