Some Accoimt of Electrical "Experiments. 263 



P. S. — Since the preceding account was drawn up, a letter 

 has been received from M. De Nelis, in which some other parti- 

 culars concerning his experiments are detailed. Speaking of the 

 radiated figures produced on a plate of glass covered with pow- 

 dered Ivcopodium; he says, that if a large pane is employed 

 coated on one side, and covered with lycopodium on the other, 

 the full charge of a jar of a square foot coated surface, conveyed 

 to the powdered side of the plate by a pointed wire, will pro- 

 duce a beautiful radiated figure of considerable si/e, in which it 

 may be distinctlv observed, that when a positive charge is em- 

 ployed, the action bv which the figure is produced proceeds from 

 the centre (that is the positive wire) to the circuniferenre ; and 

 that when a negative charge is employed the appearance is di- 

 rectly contrary, evidently proceeding from each pore of the vi^ 

 treous surface towards the negative point at its centre. This, 

 M. De Nelis observes, " appears to him to furnish much light in 

 explanation of the charge of idio-electric sul)stances by the 

 theory of molecular attraction." — It may indeed be observed, 

 that the plumose and star-like figures produced bv positive elec- 

 tricity, when contrasted with the smooth lines, dots, and balls, 

 which result from negative electricity, evince an action which 

 corresponds very accurately with the opinion that the opposite 

 electricities are respectively but the condensed and rarified 

 states of a single fluid : but the same evidence is given in a vei-y 

 similar manner by the different appearatice of positive and ne- 

 gative light; and all the varieties of Lichtenberg's figures have 

 been familiar to English electricians since the extensive experi- 

 nicnts of Mr. Bennett on that subject. 



Another experiment which M. De Nelis has lately made is 

 thus described: " Take a small pane of flint glass, and two thin 

 strips of silver, each about two or three lines wide, and so thin 

 that it mav easily bend. These strips are to be fixed on thfe 

 centre of the plate of glass by means of wax, their ends being at 

 the distance of a line from each other ; around this interval fix 

 a circle of wax one inch diameter, and a third of an inch high, 

 and fill it with olive oil, over which place a plate of glass to pre- 

 vent the oil from being thrfwvn about by bubbles of gas which 

 are always disengaged from it by the action of electricity. Place 

 this apparatus so that a current of sparks from a powerful ma- 

 chine may traverse the interval between the silver slips ; imme- 

 diately inflamed bubl)Ies of gas will appear ; and the attraction 

 of the fluid for the bases of the gla-^s is so great, that these little 

 balls of fire pass alternately over the whole surface of the silver 

 slips. If the action of a powerful current of electricity is con- 

 tinued in this way for an hour, the glass between the slips will 

 K 4 be 



