The administration of justice having been originally vested in the crown, the king in former times rode in person through the realm once in seven years, to judge and determine crimes and offences; but afterwards justices in eyre were appointed, and since that time justices of assize and gaol delivery. A commission of gaol delivery is a patent in the nature of a letter from the king to certain persons, appointing them his justices, or two or three of them, and authorizing them to deliver his gaol at a particular place of the prisoners in it; for which purpose it commands them to meet at such a place, at such time as they themselves shall appoint; and informs them, that for the same purpose the king has commanded his sheriff of the same county to bring all the prisoners of the gaol, and their attachments, before them at the day appointed.