LUMINOUS ELECTRICITY. g^ 



*l'he next day, when the excitation was very nearly, but Modification of 

 hot quite, as ftrong, it was obferved that the order- of thefe ^^"^ P^^"°""'*"2» 

 appearances could be efFe6led by the affiftance of a metallic 

 point. Plentiful bruflies were thrown out from a three inch 

 ball, but they could not be made to difappear. When a 

 pointed wire or a fmail metallic ball was prefented, the ef- ' 

 feels were as follow : 



The point being at a great diflance, the root of the brufh by the vicinity 



had a luminous circle of lambent light round it on the furface ^'^^P^'lf °^ 



° fmall ball. 



of the ball. When the point was nearer, the brulh difap- 



peared, and nothing was feen but an exceedingly bright fpeck 



on the furface of tl>e ball, which was fometimes ftatrnary and 



fometimes moved about. When the point was ftill nenrer, 



the fpeck (hrew out ramified fparks of the fecond kind, at. the 



lame time that a lambent luminous circle appeared. The fpeck 



tvas never in the center of the circle, but moved at a diftance 



round the circle, irregularly, fometimes the one way and 



fomelimes (he contrary, and was fometimes ftationary. 



Thefe two orders of bruflies were entirely the fame as thofe More particulii* 



of the day before. The luminous brufh which firft appeared jlefcriptiouofth* 

 , , - . , ^ , II 1 r 1 • 1 luminous ap» 



had a Uraight flem, then a broken or lets lummous part, be- pearances. 



yond which loofe cotton-looking fibres flew off in radial dt- 



re6lions, as at Fig. 1, PL I. The latter ramified fparks had 



a ftraight central flem, out of which well defined branches 



ifTued nearly at right angles. They much more clofely re- 



fembleda tree bare of leaves. 



The fecond brufh was not larger, but rather lefs in its di- 

 menfions than the firft. 



When the ball of four-tenths of an inch was held at a cer- All the phenc 

 tain diftance from the two and a half inch ball, when eleari- ^^'^"^^ ^'''''*''^ '* 

 fied, the firft kind of brufh was feen on the fide fartheft from 

 the fmall ball, at the fame time that the fecond kind of fpark 

 or brulh flew out towards the fmall ball, and the lambent lu- 

 niinous appearance was feen on the furface. 



Thefe are the general fafts ; but I have no doubt but they 

 would prefent many modifications upon being repeated;. 



Thefe fads may ferve to affift our meditatiom with regard Remarks on the 

 lo the nature of the eledric fpark. In a late paper by Mr. eleftric fpark, 

 Biot, given at page 21 4 of our Vol. XII. the author makes an 

 ingenious conje6lure, that the light and heat in this pheno- 

 menon may have been produced by mechanical compreffion 



Vol. Xill.— January, I SCO. K of 



