If we could tame lightning and guide it safely, its services would probably become innumerable. Lightning as man's right hand! Why not? Was it not the auxiliary of the gods in the dark ages? To-day, is it not regarded by astronomers as one of the most important forces of nature? Why should it not be the collaborator of man's intelligence to-morrow? CHAPTER IV FIREBALLS Here we penetrate into what is, perhaps, the most mysterious, and certainly the least understood domain of thunder and lightning. Among all the electrical phenomena to be observed in the atmosphere, there is nothing stranger than those fireballs of which we have already spoken, and which in form and size recall the electric lights in our Paris boulevards. Curious the contrast between electricity tamed and civilized and electricity running wild! Between the arc lights fulfilling their peaceful and useful function as substitutes for the sun, and these dread engines of destruction sowing death and havoc! It is not long since the existence of these fireballs has been acknowledged by scientists as an actual fact. Until quite recent times they were regarded as the figment of excited imaginations, and wise men smiled at the wild stories of their ravages. Their reality has now been established, however, beyond the possibility of doubt. In shape they are not always quite spherical, though this is their normal appearance; and although their contours are usually clearly defined, they are sometimes encircled by a kind of luminous vapour, such as we often see encircling the moon. Sometimes they are furnished with a red flame like a fuse that has been lit. Sometimes their course is simply that of a falling star. Sometimes they leave behind them a luminous trail which remains visible long after they themselves have disappeared. They have been described as looking like a crouching kitten, an iron bar, a large orange--so harmless apparently, that you were tempted to put out your hand to catch it. There is record of one being seen as large as a millstone. One remarkable thing about them is the slowness with which they move, and which sometimes enables their course to be watched for several minutes. In our first chapter we gave several instances of the occurrence of fireballs. Let us look at some more. Here is one taken from Arago's learned treatise upon thunder. The record is from the pen of Batti, a marine painter in the service of the Empress of Austria and resident at Milan.