2D8 ATMOSPHERIC ELECTRICITY. 



well proved, that all bodies, even which are in equilibrium 



with the earth, have electric atmofpheres in the open air, 



from which remits a modification in their electric (late. 



The ek&ric in- Air. Erman conjectured, that a body of a greater volume 



fiuence of atree rai ht h m influence. He obferved a tree which 



was ftil] greater. ° 



flood alone in an open fpace. He retired to (he diftance of 



twenty paces from it, and difcharged the electricity of his 

 electrometer by touching it with the finger. He then ap- 

 proached the tree, keeping his electrometer at the fame height 

 above the earth. The electrometer diverged negatively, and 

 the divergence continually augmented as- he came nearer, fo 

 that the leaves of gold touched the fidQs of the glafs at the 

 moment when he was under the tree. This negative ftate 

 lafted as long as he remained there, but when he retired 

 again it gradually difappeared, fo as to have become infenfible 

 when he arrived at the original diftance of twenty feet. 



When the communication between the point of the elec- 

 trometer and the earth was completed under the tree, the 

 divergence ceafed ; but the electricity was only apparently 

 deftroved, and manifefled itfelf again when he retired from 

 the tree. 

 The mutual in- Two electrometers" being brought near each other at the 

 eleaiTm^terTis diftance or ~ half a ' 00t f' rom tne earth, did not produce this 

 fcarcely feen effect, becaufe the mafs of the earth too greatly influenced 

 very , ne tT t e , that proximity. In order to have very fimple refults, it would 



earth. Remarks ... . . 



on aeioftatic ex- be requifite to di (cover fome means of rapidly elevating an 

 infulated body to fome thoufands of feet above the ground ; 

 and if this experiment were undertaken in the boat of a bal- 

 loon, it would probably be feen, that the pofitive charge 

 would conftantly increafe during the afeent, and would be- 

 come negative as it approached the earth : but if means 

 could be had of changing the fyftem of the balloon in the at- 

 inoiphere, by the intervention of another body, which would 

 be difficult, the contrary effects might be expected. This 

 change of fyftem is however feen when a cloud defcends, 

 and difcharges itfelf with exploiion into the earth. But an 

 electrometer of the ufual conftruction in the boat of a balloon 

 would indicate nothing, becaufe the upper part always has a 

 charge of electricity of (he fame kind as that of the gold- 

 leaves, and of equal intensity. 



If 



pe: tments pro- 

 posed. 



