Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

99. On the following day some of the Athenians proceeded with the construction of that part of the circle which lay towards the north;¹ others began to collect wood and stones and lay them along the intended course of the wall towards Trogilus, where the distance was shortest from the Great Harbour to the outer sea. [2] The Syracusans by the advice of their commanders, chiefly of Hermocrates, determined to risk no more general engagements. They thought it better to raise a counter-wall across the line along which the Athenian wall was building. If they were first they would intercept them. They might indeed be attacked by the Athenians while thus engaged, but then they could oppose them with a part of their army; and there would be time to run a stockade across, if not a wall, before any attack took place. [3] The Athenians on the other hand would have to leave their work, and employ their whole army against them. So they came out and drew a cross-wall, beginning at their own city, from a point below the circle of the Athenian wall,² cutting down the olive-trees in the precinct of Apollo and erecting wooden towers. [4] As yet the Athenian ships had not sailed round from Thapsus into the Great Harbour; the Syracusans were still masters of their own coast, and the Athenians brought their necessaries from Thapsus by land.