Page:Various Forces of Matter.djvu/133

of the machine is turned a certain amount of electricity is evolved, as you will see by the rise of the little straw indicator (at a). Now I know from the appearance of repulsion of the pith ball at the end of the straw that electricity is present in those brass conductors (b b), and I want you to see the manner in which that electricity can pass away [touching the conductor (b) with his finger, the Lecturer drew a spark from it, and the straw electrometer immediately fell]. There, it has all gone; and that I have really taken it away you shall see by an experiment of this sort. If I hold this cylinder of brass by the glass handle and touch the conductor with it I take away a little of the electricity. You see the spark in which it passes, and observe that the pith-ball indicator has fallen a little, which seems to imply that so much electricity is lost; but it is not lost, it is here in this brass, and I can take it away and carry it about, not because it has any substance of its own, but by some strange property which we have not before met with as belonging to any other force. Let us see whether we have it here or not. [The Lecturer brought the charged cylinder to a jet from which gas was issuing; the spark was seen