The maritime confederacy,—originally commenced at Delos, under the headship of Athens, but with a common synod and deliberative voice on the part of each member,—had now become transformed into a confirmed empire on the part of Athens, over the remaining states as foreign dependencies; all of them rendering tribute except Chios, Samos, and Lesbos. These three still remained on their original footing of autonomous allies, retaining their armed force, ships, and fortifications, with the obligation of furnishing military and naval aid when required, but not of paying tribute: the discontinuance of the deliberative synod, however, had deprived them of their original security against the encroachments of Athens. I have already stated generally the steps, we do not know them in detail, whereby this important change was brought about, gradually and without any violent revolution,—for even the transfer of the common treasure from Delos to Athens, which was the most palpable symbol and evidence of the change, was not an act of Athenian violence, since it was adopted on the proposition of the Samians. The change resulted in fact almost inevitably from the circumstances of the case, and from the eager activity of the Athenians contrasted with the backwardness and aversion to personal service on the part of the allies. We must recollect that the confederacy, even in its original structure, was contracted for permanent objects, and was permanently binding by the vote of its majority, like the Spartan confederacy, upon every individual member:[2] it was destined to keep out the Persian fleet, and to maintain the police of the Ægean. Consistently with these objects, no individual member could be allowed to secede from the confederacy, and thus to acquire the benefit of protection at the cost of the remainder: so that when Naxos and other members actually did secede, the step was taken as a revolt, and Athens only did her duty as president of the confederacy in reducing them. By every such reduction, as well as by that exchange of personal service for money-payment, which most of the allies voluntarily sought, the power of Athens increased, until at length she found herself with an irresistible navy in the midst of disarmed tributaries, none of whom could escape from her constraining power,—and mistress of the sea, the use of which was indispensable to them. The synod of Delos, even if it had not before become partially deserted, must have ceased at the time when the treasure was removed to Athens,—probably about 460 B.C., or shortly afterwards. [2] Thucyd. v. 30: about the Spartan confederacy,—εἰρημένον, κύριον εἶναι, ὅ,τι ἂν τὸ πλῆθος τῶν ξυμμάχων ψηφίσηται, ἢν μή τι θεῶν ἢ ἡρώων κώλυμα ᾖ.