we next find him serving in the Earl of Glencairn's regiment in the War of the Covenant. What part he took in it is not certainly known, but he was in command of a troop when recalled in 1641 to compete for a regency (as a tutorship or professorship was then called) in the University of Glasgow. He was elected in March. Mathematics, logic, ethics and politics were the chief subjects of his lectures, and a notebook on logic by one of his students has been preserved. His activity and skill in matters of college business were praised by his colleagues, who numbered amongst them some of the leading Covenanting divines, and his zeal in teaching was gratefully acknowledged by his students. After nearly seven years' service he resigned his regency, and removed to Edinburgh, where he was admitted to the bar on 17 February 1648. This step had probably been rendered easier by his marriage, four years before, to Margaret Ross, co-heiress of Balneil in Wigtown. Stair's practice at the bar does not appear to have been large. His talents lay rather in the direction of learning and business than of oratory or advocacy. His reputation and the confidence reposed in him were shown by his appointment in 1649 as secretary to the commission sent to the Hague to treat with Charles II by the Scots Parliament. The negotiation having been broken off through the unwillingness of the young king to accept the terms of the Covenanters, Stair was again sent in the following year to Breda, where the failure of Montrose's expedition forced Charles to change his attitude and to return to Scotland as the covenanted king. Stair had preceded him, and met him on his landing in Aberdeenshire, probably carrying with him the news of the execution of Montrose, which he had witnessed. During the Commonwealth of England, Stair continued to practise at the bar, but like most of his brethren he refused in 1654 to take the oath of allegiance to the Commonwealth. Three years later, on the death of James Learmonth, Lord Balcomie, Stair was appointed one of the Commissioners for the Administration of Justice in Scotland, on the recommendation of Monk. His appointment to the bench on 1 July 1657, by Monk, was confirmed by Oliver Cromwell on the 26th. Stair's association with the English judges at this time must have enlarged his acquaintance