304 DE SAUSSURE, READ, AND POUILLET. 



tion, occurred at New York, about 7 P. M. after 

 a showery day. The wind was from the south, 

 while the western sky was of a brassy hue, 

 through which the descending sun was perfectly 

 visible. In this state of the atmosphere, a vivid 

 streak of lightning was seen to dart from it, 

 when clouds were immediately formed that inter- 

 cepted the solar rays, as if an immense black 

 curtain had been drawn across the western sky, 

 and attended with copious precipitations of rain. 

 Several showers were thus produced by succes- 

 sive flashes of lightning ; and during their in- 

 termissions, the sky became partially transpa- 

 rent, but of a brassy hue as at first. 



Such facts afford more decisive information in 

 regard to the nature of lightning, than volumes 

 of mere speculation ; or than thousands of arti- 

 ficial experiments ; for they completely establish 

 the important fact that elastic vapour and not 

 clouds is the proximate source of atmospheric 

 electricity. Nevertheless, I shall prove by the 

 experiments of De Saussure, Read, and Pouillet, 

 that electricity may be disengaged from all 

 vapours generated by the agency of caloric, 

 whether by natural or artificial means, or by 

 combustion that it rises from the earth in a 

 latent state of combination with aqueous vapour, 

 which it maintains in the elastic form, whence 

 it may be withdrawn by conductors, and tested 

 by the electrometer. 



