Of the might of the Nile according to the Astronomers, and of its increase. What man could decide the great contention there is among the learned concerning the source and power of this river: for Alexander, who was the most powerful of the Kings, to whom the province of Memphis in Egypt made prayer, conceived a grudge against the Nile, for that he was not able to learn the truth of the aforesaid source, though he was lord of the world. And this covetousness was not only in him, but it was also found among the Kings of Egypt, and of Persia, and of Macedonia, and of Greece. But we will here describe in some small measure the course of this river, according to the Astronomers, who say that Mercury is the source of power over the waters, and that he hath influence over them; and that when he is in that part of the heaven where the stars of the sign of Leo are in conjunction with the stars of the sign of Cancer, or with the star Sirius, to wit, that which is called the Dog star,[BF][N151] whence those days are called the Dog days, he poureth out flames full of fury from his mouth, and altereth thereby the circle of the year, and the weather also changeth, for then the summer endeth and autumn beginneth. And again, when the signs of Capricorn and Cancer are in conjunction, under which the outflow of the Nile is hidden, and when the star of Mercury is in conjunction with those signs, Mercury being lord of the waters, striketh on the mouths, that is to say, in those parts through which the Nile floweth, being under the fire of his constellation; then the Nile openeth its fount and floweth forth; and even as the sea waxeth with the waxing of the moon, so riseth the Nile as if Mercury commanded it, and increaseth till it covereth the land whence Egypt hath all its principal nutriment. And it doth not gather its waters together, nor return into its bed until the night hath as many hours as the day. And in old time there were some who said that the rising of this stream was chiefly because of the snows of Ethiopia, but this we find is not so, for the north doth not look upon those mountains of Ethiopia; no, not any one of the Bears of either pole, to wit, Ellice and Cynosure,[N152] neither the greater nor the less, which bring the chill and are the cause of snows and frosts; nor doth the north-east wind,[BG] which bringeth the frost with it. [Footnote BF: Canicolla.] [Footnote BG: Blow upon these mountains.]