Let us begin, then, by clearly disembarrassing our minds of any lingering belief in the existence of thunderbolts. There are absolutely no such things known to science. The two real phenomena that underlie the fable are simply thunder and lightning. A thunderstorm is merely a series of electrical discharges between one cloud and another, or between clouds and the earth; and these discharges manifest themselves to our senses under two forms--to the eye as lightning, to the ear as thunder. All that passes in each case is a huge spark--a commotion, not a material object. It is in principle just like the spark from an electrical machine; but while the most powerful machine of human construction will only send a spark for three feet, the enormous electrical apparatus provided for us by nature will send one for four, five, or even ten miles. Though lightning when it touches the earth always seems to us to come from the clouds to the ground, it is by no means certain that the real course may not at least occasionally be in the opposite direction. All we know is that sometimes there is an instantaneous discharge between one cloud and another, and sometimes an instantaneous discharge between a cloud and the earth. But this idea of a mere passage of highly concentrated energy from one point to another was far too abstract, of course, for primitive man, and is far too abstract even now for nine out of ten of our fellow-creatures. Those who don't still believe in the bodily thunderbolt, a fearsome aerial weapon which buries itself deep in the bosom of the earth, look upon lightning as at least an embodiment of the electric fluid, a long spout or line of molten fire, which is usually conceived of as striking the ground and then proceeding to hide itself under the roots of a tree or beneath the foundations of a tottering house. Primitive man naturally took to the grosser and more material conception. He figured to himself the thunderbolt as a barbed arrowhead; and the forked zigzag character of the visible flash, as it darts rapidly from point to point, seemed almost inevitably to suggest to him the barbs, as one sees them represented on all the Greek and Roman gems, in the red right hand of the angry Jupiter. The thunderbolt being thus an accepted fact, it followed naturally that whenever any dart-like object of unknown origin was dug up out of the ground, it was at once set down as being a thunderbolt; and, on the other hand, the frequent occurrence of such dart-like objects, precisely where one might expect to find them in accordance with the theory, necessarily strengthened the belief itself. So commonly are thunderbolts picked up to the present day that to disbelieve in them seems to many country people a piece of ridiculous and stubborn scepticism. Why, they've ploughed up dozens of them themselves in their time, and just about the very place where the thunderbolt struck the old elm-tree two years ago, too.