John N. Olvey, of Oaklandon, a prisoner in the Prison North, discharged under the poor-convict act day before yesterday, was, previous to going to prison, a confirmed opium-eater, often taking as much as ten grains of morphine, enough to kill half a dozen men, at a dose. Of course he was, after the first few weeks, during which time the quantity given him was gradually reduced to none at all, deprived of the drug and comes back cured of one bad habit, at least.