I
1
2
3
To come now to my purpose—listen to the explanation offered by Natural Philosophy concerning the Fires which the atmosphere drives athwart. Their oblique course and amazing velocity furnish proof that they are thrust out with great violence. Evidently they do not come forth of themselves, they are shot out. There are many different forms of them. A certain kind of them Aristotle calls a She-Goat. If you ask me why, I must retort by asking you first to explain why they are also called Kids. It will, perhaps, be more to the purpose not to cross-examine one another with questions such as: What does such and such an author say? Answer me. Better examine the cause of the phenomenon itself than form surmises as to why Aristotle has applied the name She-Goat to a ball of fire. This was the shape of the one as big as the moon that appeared when Paulus was engaged in the war against Perseus. In our own days we have more than once seen a huge ball-shaped flame which broke up in the very middle of its course. We saw a similar portent about the time of the death of the late Emperor Augustus. We again saw one when Sejanus was executed. A warning of the same kind preceded the death of Germanicus.
4
You may, perhaps, exclaim: Are you then so benighted as to suppose that the gods send out previous intimation of the death of great men? Do you imagine that anything on earth is so great that the Universe should perceive its loss? That question must be reserved for another season. We shall then see whether a fixed succession is observed in all events, and whether one event is so bound up with another that what precedes is either cause or at least token of what follows. We shall then see, too, whether the gods trouble themselves about human concerns, and whether the mere series of events reveals by unmistakable signs what its effects must be. Meantime, I venture the opinion that fires of the class referred to are produced by violent friction of the atmosphere. The pressure inclines toward one or other side, and as there is no yielding there, an internal struggle ensues. From violent action of this kind arise the different varieties of fires—beams, balls, torches, and gleams. When the shock is less severe, and the atmosphere is merely grazed, as it were, smaller lights are emitted,
And the flying stars drag their hairy tail.
5
Then their thin fires mark a slender path, which they prolong across the sky. For that reason no night is without sights of the kind; no great movement of the atmosphere is required to produce them. In fact, to put it shortly, they are due to the very same cause as thunderbolts, only they require less force.
6
7
8
Clouds that encounter each other with little force cause flashes of lightning; if impelled by greater violence, thunderbolts. Aristotle offers the following explanation: The earth gives forth many different exhalations, some moist, some dry, some cold, some containing the seeds of fire. And little wonder if the earth’s evaporation is of all varied kinds. Why, even in the heavens the colour of objects does not show uniform; the red of the Dog-star is brighter, that of Mars duller; Jupiter has no red, his sheen is prolonged into pure light. Well, in the great abundance of minute bodies emitted by the earth and driven up to the higher regions, of necessity some of the elements that reach the clouds furnish material for fires. They do not require any collision in order to burn, the breath of the sun’s rays is sufficient to kindle them. So with us, shavings sprinkled with sulphur catch fire at some distance. Probably, therefore, tinder of this kind gathering within the clouds is easily kindled; greater or less fires are produced just as there has been more or less substance in the elements.
9
10
11
On the other hand, to suppose either that actual stars fall or leap across the sky, or that some portion of them is taken away or pared off, is sheer folly. If this had been so, they would ere this have disappeared. For there is not a single night on which there is not a very large number of stars that seem to break up as they pass across the sky. Yet they are all found again in their wonted places: each one maintains its size unimpaired. It follows, therefore, that the fires referred to have their origin below the stars, and that, being without solid foundation on fixed abode, they quickly perish. Why, then, you ask, do they not cross the sky by day as well as by night? The next thing you will say will be that there are no stars by day because they are not visible! The stars are, of course, there, but obscured by the sun’s brightness. Similarly, meteor fires like torches cross the sky by day too, but they are hidden by the brightness of the daylight. If, as sometimes happens, a burst of light shoots out strong enough to assert its brilliance even in the face of day, then they do become visible. In fact, our own age has more than once seen torches by day, some rushing from east to west, others from west to east.
12
13
14
Sailors consider it a sign of storm when there are many shooting stars. If their appearance really is a sign of wind, they must occur in the quarter where wind is found, in other words, in the atmosphere which lies between the earth and the moon. In violent storms at sea there sometimes appear, as it were, stars settling on the sails. The sailors who are in jeopardy then suppose that they are being aided by the power of Castor and Pollux. They have really ground for better hope in this appearance, because it makes plain that the storm is breaking, and the wind falling. Otherwise the fires would flit about without settling. When Gylippus was on the voyage to Syracuse, a star appeared, resting on the very tip of his lance. In the camp of the Romans at times pikes appeared to be on fire, no doubt because fires of this kind glided down on to them: these fires are often wont to strike animals and trees, just like thunderbolts. If, however, they are discharged with less force, they merely glide down and settle, and do not inflict stroke or wound. Again, some are forced out from among clouds, others come from a clear sky, if the atmosphere has got into a condition to emit fire. In like manner, it occasionally thunders with a clear sky, and from the same cause as with a cloudy one, the atmosphere undergoing internal collision. Even when the air is comparatively clear and dry, it may become condensed, and form bodies similar to clouds, the clashing of which causes the sound of the thunder. From time to time, therefore, arise meteors like beams and like shields, and the semblance of vast fires over the sky, if a force similar in kind but greater in degree encounter suitable material.