Were Argus's eyes gradual or all at once? Argus has 100 eyes, 50 awake and 5 sleeping all the time. That way, he would be able to keep guard constantly. But would Argus's eyes have a set time to fall asleep, like 50 immediately going to sleep and 50 immediately coming awake? Or would he have one eye going, right as another would come awake?

Who says half of his eyes were asleep and half awake?

While a number of sources refer to his eyes taking sleep in turns, the only source I can find that specifies how many slept at once is Ovid:

> Argus, Aristorides, whose head was circled with a hundred glowing eyes; of which but two did slumber in their turn whilst all the others kept on watch and guard.
> Ovid's Metamorphoses I, 622-641

Also, when he is being lulled to sleep by Hermes, more of his eyes close gradually, rather than as a unit:

> but Argus strove his languor to subdue, and though some drowsy eyes might slumber, still were some that vigil kept.
> Ovid's Metamorphoses I, 682-688