and died on 9 Aug. 1765, when he was succeeded by his eldest son, James Erskine, then only three years old, whose education and career were carefully watched and forwarded by his maternal uncle, the celebrated Alexander Wedderburn.
Erskine was educated at the Edinburgh Academy, and entered the army as a cornet in the 1st horse grenadier guards, afterwards the 1st life guards. He was rapidly promoted, and became lieutenant first in the 38th regiment, and then in the 2nd dragoons, or Scots greys, in 1778, and captain in the 19th light dragoons in 1780, from which he was transferred to the 14th light dragoons in 1781. In the following year he was appointed aide-de-camp to the viceroy of Ireland and assistant adjutant-general in that kingdom, and in 1783 he was promoted major into the 8th light dragoons. In 1781 he had been elected M.P. for Castle Rising through the influence of his uncle, who had become lord chief justice of the court of common pleas, and been created Lord Loughborough in the previous year. Erskine exchanged his seat of Castle Rising for Morpeth in 1784, and soon made himself some reputation in the House of Commons as the representative of his uncle's opinions. He was chosen one of the managers of the impeachment of Warren Hastings, and while Lord Loughborough was intriguing for the chancellorship he voted against the measures of Pitt. On 9 June 1789 he took the name of St. Clair in addition to his own, on succeeding, on the death of Colonel Paterson St. Clair, to the estates of his grandmother, the Hon. Catherine St. Clair, who had married Sir John Erskine, third baronet, and in 1790 he was elected M.P. for the Kirkcaldy burghs, a seat which he held until his succession to the peerage. On 14 March 1792 Erskine was promoted lieutenant-colonel into the 12th light dragoons, and in the following year, in which his uncle became lord chancellor, he abandoned politics as an active pursuit and devoted himself to his profession. He was first sent to the Mediterranean in that year to act as adjutant-general to the army under Sir David Dundas before Toulon, and served in that capacity at Toulon, and in the subsequent operations in Corsica, including the capture of Calvi and of San Fiorenze. He was appointed aide-de-camp to the king and promoted colonel on 28 May 1795, and was in the following year sent to Portugal with the temporary rank of brigadier-general to act as adjutant-general to lieutenant-general the Hon. Sir Charles Stuart [q. v.], commanding the army in that country. He was promoted major-general on 1 Jan. 1798, and continued to serve under Sir Charles Stuart, to whom he was second in command at the capture of Minorca in that year, and whom he succeeded as commander-in-chief in the Mediterranean. He returned to England on the arrival of Sir Ralph Abercromby at the close of 1799, and was appointed colonel of the Sussex fencible cavalry, which regiment was, however, reduced in 1800. He commanded a division in Scotland from November 1800 till December 1801, when he was made colonel of the 9th light dragoons, and again from June 1803 to 1 Jan. 1805, when he was promoted lieutenant-general. Two days afterwards, on 3 Jan. 1805, he succeeded his uncle, the ex-lord chancellor, as second Lord Loughborough and second Earl of Rosslyn, under special clauses in the patents conferring those honours upon him in 1795 and 1801. On his promotion he was transferred to the Irish staff, where he commanded the south-western district until 1806, when he was sent on his celebrated special mission to Lisbon with General J. G. Simcoe. The mission was to report whether the British government should actively assist the Portuguese against Napoleon, and the result of that report was the despatch of Sir Arthur Wellesley to the Peninsula. Rosslyn was unable to accept a command there on account of his seniority to Sir Arthur Wellesley, though after the death of Sir John Moore his name was mentioned as his possible successor, because of his previous knowledge of the country in 1796. He commanded a division under Lord Cathcart in Denmark in 1807, and under Lord Chatham in the Walcheren in 1809. He commanded the south-eastern district, with his headquarters at Canterbury, from 1812 to 1814, in which year he was promoted general, and then he again turned his attention to politics. He was a strong tory of the old school, and an intimate friend of the Duke of Wellington. He acted as whip to the tory party in the House of Lords for many years, though his sentiments in favour of catholic emancipation had been known ever since 1807. He was largely rewarded with honours, and was, among other rewards, made an extra G.C.B. on the accession of George IV, and lord-lieutenant of Fifeshire. After the Duke of Wellington came into office as prime minister, Rosslyn entered the cabinet as lord privy seal, and was sworn of the privy council. He was also lord president of the council in the Duke of Wellington's short-lived cabinet of December 1834. He died on 18 Jan. 1837, at Dysart House, Fifeshire, at the age of seventy-five.
[Royal Military Calendar; Gent. Mag. April 1837.]
