Adam Clarke on Acts 27:1

And when it was determined, etc. - That is, when the governor had given orders to carry Paul to Rome, according to his appeal; together with other prisoners who were bound for the same place.

We should sail - By this it is evident that St. Luke was with Paul; and it is on this account that he was enabled to give such a circumstantial account of the voyage.

Julius, a centurion of Augustus' band - Lipsius has found the name of this cohort on an ancient marble; see Lips. in Tacit. Hist. lib. ii. The same cohort is mentioned by Suetonius, in his life of Nero, 20.