[13] Professor Tait, On Thunderstorms, Nature, vol. xxii., pp. 436-7. [14] See note at the end of this Lecture, p. 26. [15] See Tomlinson, The Thunderstorm, pp. 87-9. [16] See Tait on Thunderstorms, Nature, vol. xxii., p. 436. LECTURE II. LIGHTNING CONDUCTORS. The effects of lightning, on the bodies that it strikes, are analogous to those which may be produced by the discharge of our electric machines and Leyden jar batteries. When the discharge of a battery traverses a metal conductor of sufficient dimensions to allow it an easy passage, it makes its way along silently and harmlessly. But if the conductor be so thin as to offer considerable resistance, then the conductor itself is raised to intense heat, and may be melted, or even converted into vapor, by the discharge. On opposite page is shown a board on which a number of very thin wires have been stretched, over white paper, between brass balls. The wires are so thin that the full charge of the battery before you, which consists of nine large Leyden jars, is quite sufficient to convert them in an instant into vapor. I have already, on former occasions, sent the charge through two of these wires, and nothing remains of them now but the traces of their vapor, which mark the path of the electric discharge from ball to ball. At the present moment the battery stands ready charged, and I am going to discharge it through a third wire, by means of this insulated rod which I hold in my hand. The discharge has passed; you saw a flash, and a little smoke; and now, if you look at the paper, you will find that the wire is gone, but that it has left behind the track of its incandescent vapor, marking the path of the discharge. [Illustration: DISCHARGE OF LEYDEN JAR BATTERY THROUGH THIN WIRES.]