So obvious was the value of these fiery beacons, and so impossible did it seem to the ancient mariner to navigate the dangerous seas without their help, that he was led to ascribe their origin to supernatural wisdom. According to the Greeks, they were invented by Hercules. There is good reason to believe, however, that long before the ocean was furrowed by a Greek keel, light-towers or fire-beacons had been erected by the Libyans and the Cuthites along the low and perilous shores of Lower Egypt. During the day they served as landmarks, and during the night as beacons. Their purpose being essentially sacred, they were also used as temples, and dedicated to the gods. Regarded by the seaman with reverence as well as gratitude, he enriched them with costly offerings. Some authorities suppose that charts of the Mediterranean coast and of the channels of the Nile were painted on their walls, and that these charts were afterwards transferred to sheets of papyrus. The priests in charge of them taught the sciences of hydrography and pilotage, and how to steer a vessel's course by the aid of the stars and planets. On the summit a fire was ever burning; the fuel being placed in a machine of iron or bronze, composed of three or four branches, each representing a dolphin or some other marine animal, and all connected by decorative work. The machine was fastened to the extremity of a strong pole or shaft, like a mast, and so placed that its radiance was mainly directed seaward. [Sidenote: Homer and the fire-towers.] The impression which the fire-towers produced on the mind is finely described by Homer in a well-known passage of the "Iliad:"-- "As to seamen o'er the wave is borne The watch-fire's light, which, high among the hills, Some shepherd kindles in his lonely fold." It is said that the first regular pharos, or light-tower, was erected by one Lesches, on the Sigæan promontory, at the mouth of the Hellespont.