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ef the electric fluid, ranged in rows from the point to the knobof the wire. If there be as many millions, it will make nodifference in the conclusion to be drawn from the experiment.As there is said to be a repulsive quality (see Prop. I. p. 23.)between the electricity of the excited tube and the inherent particlesof the electric effluvia peculiar to the wire, they must act by thefollowing regular method, viz. bring the excited tube near thepointed end of the wire, the particles of the electric atmosphereon the excited tube must, as soon as they come in contact withthe first particles of the electric fluid at the point of the wire,or before, repel them. The repellency will be mutual; but asthe velocity of the particles of the excited electricity is greaterthan the particles of the electricity peculiar to the insulated wire,the weakest must recede. The first particle being drove back,; must repel the second, the second the third, and so on till youcome to the nine hundred and ninety-ninth, and that will re-pel the thousandth, and force it down the thread of the elec-trometer. As you advance with the excited tube, the particlesmust still recede, till a sufficient quantity force the two balls of

the electrometer to diverge with positive electricity 8 . I willsuppose that 500 of the electric particles are driven from thewire by the repellency of the atmosphere of the excited tube,into the electrometer; and that the other 500 remain upon thepart of the wire farthest from the excited tube. Upon remov-ing the tube at some distance from the wire, it is said the elec-tric fluid returns, and the equilibrium is restored in the wire. Ishould be glad to be informed by what law of motion this is done ?

9 All matter perseveres in its state of rest, or of uniform

* See Proposition III. p. 4.

* Principia, p. }g. Newton’s first law of motion.

E 2

motion.