The first of these passes was called Tempe, and a body of troops was sent to guard it; but they found that this was useless and impossible, and came back again. The next was at Thermopylæ. Look in your map of the Archipelago, or Ægean Sea, as it was then called, for the great island of Negropont, or by its old name, Euboea. It looks like a piece broken off from the coast, and to the north is shaped like the head of a bird, with the beak running into a gulf, that would fit over it, upon the main land, and between the island and the coast is an exceedingly narrow strait. The Persian army would have to march round the edge of the gulf. They could not cut straight across the country, because the ridge of mountains called Oeta rose up and barred their way. Indeed, the woods, rocks, and precipices came down so near the seashore, that in two places there was only room for one single wheel track between the steeps and the impassable morass that formed the border of the gulf on its south side. These two very narrow places were called the gates of the pass, and were about a mile apart. There was a little more width left in the intervening space; but in this there were a number of springs of warm mineral water, salt and sulphurous, which were used for the sick to bathe in, and thus the place was called Thermopylæ, or the Hot Gates. A wall had once been built across the westernmost of these narrow places, when the Thessalians and Phocians, who lived on either side of it, had been at war with one another; but it had been allowed to go to decay, since the Phocians had found out that there was a very steep narrow mountain path along the bed of a torrent, by which it was possible to cross from one territory to the other without going round this marshy coast road. This was, therefore, an excellent place to defend. The Greek ships were all drawn up on the further side of Euboea to prevent the Persian vessels from getting into the strait and landing men beyond the pass, and a division of the army was sent off to guard the Hot Gates. The council at the Isthmus did not know of the mountain pathway, and thought that all would be safe as long as the Persians were kept out of the coast path.