86 Biographical Account of [Feb. 



They granted the identity of lightning and the electric fluid, 

 the experiment of Marly la Ville having decided the point ; 

 but the small number of sparks which proceeded from the 

 rod made them doubt the possibility of extricating the 

 immense quantity of matter contained in a cloud. Even 

 the dangerous experiments of Romas de Nerac did not 

 satisfy them ; but the melancholy death of Richman, on the 

 6th August 1753, by the electric fluid which was conducted 

 by the string of a kite which he was raising, convinced 

 them of the fact, and enabled them they conceived to 

 explain a passage in Pliny, where the naturalist relates that 

 Tullus Hostilius was killed by lightning for having been 

 irregular in the performance of ceremonies, in consequence 

 of his predecessor Numa causing thunder to descend from 

 heaven. Subsequently, disputes occurred with regard to 

 the propriety of using thunder-rods with sharp points or 

 with nobs. # Lemonnier, in 1752, discovered that electricity 

 existed in the atmosphere, not only during storms, but 

 when the sky was perfectly clear. He observed also, that 

 in clear weather it underwent regular variations of intensity ; 

 and Beccaria established the fact that in all seasons, at all 

 heights, and during all winds, the electricity in clear 

 weather is constantly positive or vitreous. 



For a considerable period after the Leyden phial had 

 been discovered, the electrometer was not thought of. Darey 

 and Le Roy, in 1749, invented one, and in 1752 Nollet pro- 

 posed an instrument consisting of two threads, which, after 

 being electrified by the effect of repulsion, separated like 

 the legs of a pair of compasses. 



Cavallo, in 1780, realized what Nollet had only projected. 

 His threads were of metal, and bore at their extremities 

 spheres formed of the pith of the elder. Volta substituted 

 for the pith dried straws. His letter to Lichtenberg in 

 1786, in which he established, by numerous experiments, 

 the properties of electrometers formed with straws, contains 

 a description of the method by which these instruments 

 may be compared ; of the intensity of the greatest charges, 



* I have omitted in the text to mention the observation of M. Arago, that the 

 circumstance of George III. taking part with those who recommended rods with 

 nobs, against Franklin, who advocated the use of pointed conductors, is to be 

 considered an important incident in the history of the American Revolution. — Edit. 



