In order distinctly to understand these movements, it is necessary that the reader should first have a clear conception of the geographical conformation of the coasts and seas along which the path of the expedition lay. By referring to the map of Greece, we shall see that the course which the fleet would naturally take from Therma to the southeastward, along the coast, was unobstructed and clear for about a hundred miles. We then come to a group of four islands, extending in a range at right angles to the coast. The only one of these islands with which we have particularly to do in this history is the innermost of them, which was named Sciathus. Opposite to these islands the line of the coast, having passed around the point of a mountainous and rocky promontory called Magnesia, turns suddenly to the westward, and runs in that direction for about thirty miles, when it again turns to the southward and eastward as before. In the sort of corner thus cut off by the deflection of the coast lies the long island of Euboea, which may be considered, in fact, as almost a continuation of the continent, as it is a part of the same conformation of country, and is separated from the main land only by submerged valleys on the north and on the east. Into these sunken valleys the sea of course flows, forming straits or channels. The one on the north was, in ancient times, called Artemisium, and the one on the west, at its narrowest point, Euripus. All these islands and coasts were high and picturesque. They were also, in the days of Xerxes, densely populated, and adorned profusely with temples, citadels, and towns. On passing the southernmost extremity of the island of Euboea, and turning to the westward, we come to a promontory of the main land, which constituted Attica, and in the middle of which the city of Athens was situated. Beyond this is a capacious gulf, called the Saronian Gulf. It lies between Attica and the Peloponnesus. In the middle of the Saronian Gulf lies the island of AEgina, and in the northern part of it the island of Salamis. The progress of the Persian fleet was from Therma down the coast to Sciathus, thence along the shores of Euboea to its southern point, and so round into the Saronian Gulf to the island of Salamis. The distance of this voyage was perhaps two hundred and fifty miles. In accomplishing it the fleet encountered many dangers, and met with a variety of incidents and events, which we shall now proceed to describe.