From here he marched through the province of Babylon, which immediately submitted to him, and was much surprised at the sight in one place where fire issues in a continuous stream, like a spring of water, out of a cleft in the earth, and the stream of naphtha, which, not far from this spot, flows out so abundantly as to form a sort of lake. This naphtha, in other respects resembling bitumen, is so subject to take fire, that before it touches the flame, it will kindle at the very light that surrounds it, and often inflame the intermediate air also. The barbarians, to show the power and nature of it, sprinkled the street that led to the king's lodgings with little drops of it, and when it was almost night, stood at the further end with torches, which being applied to the moistened places, the first at once taking fire, instantly, as quick as a man could think of it, it caught from one end to another, in such a manner that the whole street was one continuous flame. Alexander, in his own letters, has given us an account of his war with Porus. He says that two armies were separated by the river Hydaspes, on whose opposite bank Porus continually kept his elephants in order of battle, with their heads towards their enemies, to guard the passage; that he, on the other hand, made every day a great noise and clamor in his camp, to dissipate the apprehensions of the barbarians; that one stormy, dark night he passed the river, at a distance from the place where the enemy lay, into a little island, with part of his foot, and the best of his horse. Here there fell a most violent storm of rain accompanied with lightning and whirlwinds, and although he saw some of his men burnt and dying with the lightning, he nevertheless quitted the island and made over to the other side. Here, apprehending the multitude of the enemy, and to avoid the shock of their elephants, he divided his forces, and attacked their left wing himself, commanding Coenus to fall upon the right, which was performed with good success. By this means both wings being broken, the enemies fell back in their retreat upon the centre, and crowded in upon their elephants. There rallying, they fought a hand to hand battle, and it was the eighth hour of the day before they were entirely defeated.