But it was the introduction and general employment of lightning-rods that dealt a final deathblow to the thunderbolt theory.  A lightning-conductor consists essentially of a long piece of metal, pointed at the end whose business it is, not so much (as most people imagine) to carry off the flash of lightning harmlessly, should it happen to strike the house to which the conductor is attached, but rather to prevent the occurrence of a flash at all, by gradually and gently drawing off the electricity as fast as it gathers before it has had time to collect in sufficient force for a destructive discharge.  It resembles in effect an overflow pipe which drains off the surplus water of a pond as soon as it runs in, in such a manner as to prevent the possibility of an inundation, which might occur if the water were allowed to collect in force behind a dam or embankment.  It is a flood-gate, not a moat:  it carries away the electricity of the air quietly to the ground, without allowing it to gather in sufficient amount to produce a flash of lightning.  It might thus be better called a lightning-preventer than a lightning-conductor:  it conducts electricity, but it prevents lightning.  At first, all lightning-rods used to be made with knobs on the top, and then the electricity used to collect at the surface until the electric force was sufficient to cause a spark.  In those happy days, you had the pleasure of seeing that the lightning was actually being drawn off from your neighbourhood piecemeal.  Knobs, it was held, must be the best things, because you could incontestably see the sparks striking them with your own eyes.  But as time went on, electricians discovered that if you fixed a fine metal point to the conductor of an electric machine it was impossible to get up any appreciable charge because the electricity kept always leaking out by means of the point.  Then it was seen that if you made your lightning-rods pointed at the end, you would be able in the same way to dissipate your electricity before it ever had time to come to a head in the shape of lightning.  From that moment the thunderbolt was safely dead and buried.  It was urged, indeed, that the attempt thus to rob Heaven of its thunders was wicked and impious; but the common-sense of mankind refused to believe that absolute omnipotence could be sensibly defied by twenty yards of cylindrical iron tubing.  Thenceforth the thunderbolt ceased to exist, save in poetry, country houses, and the most rural circles; even the electric fluid was generally relegated to the provincial press, where it still keeps company harmoniously with caloric, the devouring element, nature’s abhorrence of a vacuum, and many other like philosophical fossils:  while lightning itself, shorn of its former glories, could no longer wage impious war against cathedral towers, but was compelled to restrict itself to blasting a solitary rider now and again in the open fields, or drilling more holes in the already crumbling summit of Mount