[ 1+2 J 



wider, and (till wider when it diiTolved into rain j but 

 their repelling power became greatest in proportion as 

 the drops increafed. 



The electrometer placed out from a garret window 

 ("p< 138.), has been frequently ufeful to me, in de- 

 termining the nature of an approaching cloud, whofe- 

 electricity, although generally ftrong, was for the 

 mo(t part uncertain, having been fometimes pcjitive,.. 

 and at other times negative. But, as the wind or 

 rain were frequent impediments to the accuracy of my 

 experiments, the following methods of making obfer- 

 Vations, with fuccefs, under (belter, occurred to me. 



I have fometimes flood, in an upper room, on a 

 cake of wax, holding in my right hand, out at the 

 window, a long (lender piece of wood, round which 

 a wire projecting a few inches had been twifted, and 

 in my left hand an electrometer : an affiftant had ex- 

 cited glafs or wax in readinefs. 



At other times, I have made ufe of a tapering, 

 tube of tin, twenty feet long, ending in a point; the 

 greateft part of it ftood out high in the air, and the 

 thick endj from which an electrometer hung, was 

 fupported infide. the window, fometimes with (ilk. 

 cords, and at other times with ftrong fticks of fealing- 

 wax, fuftained at either end by hooks of iron- wire. , 



By either of thefe means I have often difcovered,, 

 that what feemed to me a (ingle cloud, produced, in, 

 its paffing over, feveral fuccetfive changes, frompo-- 

 fitive to .negative, and from negative-, to pojitive elec- 

 tricity, the balls coming together each time, and re- - 

 ma'ining in contact a few feconds, . before they re~ 

 pelled each other again,. 



