502 ELECTRICITY. 



its crossing the earth's orbit, but in going ten miles, it 

 would occupy only the two millionth part of a second, 

 a period altogether imperceptible to man. 



The following extracts from the Article on Electricity 

 contained in the English Library of Useful Knowledge, 

 state some interesting particulars in relation to this part 

 of our subject. 



' By accurate experiments it appears that the force of 

 the electric shock is weakened, that is, its effects are di- 

 minished, by employing a conductor of great length for 

 making the discharge. But it is difficult to assign a 

 limit to the number of persons through which even a 

 small charge of electricity may be sent, so that all shall 

 experience the shock ; or to the distance along which it 

 may be conveyed by good conductors. 



' At an early period of electrical inquiries, much in- 

 terest was attached to the determination of these points. 

 The Abbe Nollet passed an electrical shock from a small 

 phial through a hundred and eighty of the French guards 

 in the presence of the king ; and at the Carthusian con- 

 vent in Paris, the monks were formed into a line above a 

 mile in length, by means of iron wires held between 

 them ; on the discharge of the jar the sensation was felt 

 at the same moment by all the persons composing this 

 vast circuit. Many experiments were made both by the 

 English and French electricians with a view to ascertain 

 the space which a discharge can be made to traverse, 

 and the velocity with which it is transmitted. Of these 

 the most ingenious and satisfactory were the experiments 

 planned and executed by Dr Watson, with the assistance 

 of the leading members of the Royal Society. A cir- 

 cuit was formed by a wire which extended the whole 

 length of Westminster bridge, at a considerable height 

 above the river; one end of this wire communicated with 

 the outer coating of a charged phial or jar, the other be- 

 ing held by a person on the opposite side of the river, 

 who formed a communication with the water by dipping 

 into it an iron rod held by the other hand. The circuit 

 was completed by another person, who stood near the 

 phial, and who likewise dipped an iron rod into the river 

 with one hand, and was enabled by means of a wire held 



