back into the city without venturing to engage; merely leaving a body of horse to harass the operations of the besiegers, and constrain them to keep in masses. The newly-acquired Athenian cavalry, however, were here brought for the first time into effective combat. With the aid of one tribe of their own hoplites, they charged the Syracusan horse, drove them off with some loss, and erected their trophy. This is the only occasion on which we read of the Athenian cavalry being brought into conflict; though Nikias had made the absence of cavalry the great reason for his prolonged inaction. [371] Thucyd. vi, 98. ἐχώρουν πρὸς τὴν Συκῆν οἱ Ἀθηναῖοι, ἵναπερ καθεζόμενοι ἐτείχισαν τὸν κύκλον διὰ τάχους. [372] The Athenians seem to have surpassed all other Greeks in the diligence and skill with which they executed fortifications: see some examples, Thucyd. v, 75-82; Xenoph. Hellen. iv, 4, 18. Interruption being thus checked, Nikias continued his blockading operations; first completing the Circle,[373] then beginning his wall of circumvallation in a northerly direction from the Circle towards Trogilus: for which purpose a portion of his forces were employed in bringing stones and wood, and depositing them in proper places along the intended line. So strongly did Hermokratês feel the inferiority of the Syracusan hoplites in the field, that he discouraged any fresh general action, and proposed to construct a counter-wall, or cross-wall, traversing the space along which the Athenian circumvallation must necessarily be continued so as to impede its farther progress. A tenable counter-wall, if they could get time to carry it sufficiently far to a defensible terminus, would completely defeat the intent of the besiegers: but even if Nikias should interrupt the work by his attacks, the Syracusans calculated on being able to provide a sufficient force to repel them, during the short time necessary for hastily constructing the palisade, or front outwork. Such palisade would serve them as a temporary defence, while they finished the more elaborate cross-wall behind it, and would, even at the worst, compel Nikias to suspend all his proceedings and employ his whole force to dislodge them.[374] [373] Dr. Arnold, in his note on Thucyd. vi, 98, says that the Circle is spoken of, in one passage of Thucydidês, as if it had _never been completed_. I construe this one passage differently from him (vii, 2, 4)—τῷ ἄλλῳ τοῦ κύκλου πρὸς τὸν Τρώγιλον ἐπὶ τὴν ἑτέραν θάλασσαν: where I think τῷ ἄλλῳ τοῦ κύκλου is equivalent to ἑτέρωθι τοῦ κύκλου, as plainly appears from the accompanying mention of Trogilus and the northern sea. I am persuaded that the Circle was finished; and Dr. Arnold himself indicates two passages in which it is distinctly spoken of as having been completed.