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in the center between the glasses; let it be of the fame heightwith them, and connected with a chain to the conductor of theelectrical machine. Upon the four glasses, and the wire, lay apane of glass twenty inches, or two feet square, with the centerof the pane upon the point of the wire.

When the apparatus is thus prepared, turn the cylinder of themachine, and if the foregoing property ascribed to the glass ex-ists, the electric effluvia cannot spread upon the surface of thepane, very far beyond the point of the wire. To discover whe-ther the electric fluid has reached the extremities of the pane,present a feather, or a pith-ball, suspended with a flaxen thread,cither near the angles, or sides of the pane, and it will be in-stantly attracted to the glass, and there remain as long as youturn the cylinder of the machine. If you present the back ofyour hand near the angles of the pane, you may feel the electriceffluvia passing off from the glass, and if you darken the room,you may fee them z which is as strong a proof as a reasonableperson can desire, that the electric effluvia move on the surface ofthe glass, and from the center where the wire is fixed, to theextremities of the pane.

I (hall endeavour to obviate any controversy on this point, bythe addition of another experiment under this head, which ap-pears to carry demonstration with it.

E x p E R I M E n. t IL

Take a glass tube, four feet long (I have not a longer, or Iwould have used it) fix it in a metal foot perpendicular to thehorizon, and connect it with either a wire, or a chain, reachingfrom the top of the glass tube to the conductor of the electricalr - machine.