In 1772, he was advanced to the rank of commander in the Scorpion of fourteen guns. In the spring of 1775, he was made post-captain on board the Marlborough, seventy-four guns, and soon after he obtained, first, the command of the Pearl, and then of the Perseus frigate. In the Perseus, which was remarkable as the first ship in the British navy that was sheathed with copper, he made a conspicuous figure, during the early years of the contest with America, as an active and intrepid officer on the coast of that country, under lord Howe and admiral Arbuthnot. He was likewise often engaged in the services, in this unhappy war, where sea and land forces were united—in particular at the reduction of Charleston, he conducted himself with such gallantry in the command of a detachment of seamen, as to gain frequent and most honourable mention in the official despatches of general Sir Henry Clinton The experience which he thus acquired was of great service to him long afterwards, when he had a more prominent and distinguished part to perform.

In 1780, having returned to England with despatches from admiral Arbuthnot, he was, on his arrival, appointed to the command of the Warwick of fifty guns. In the general election, which took place this year, he was chosen member of parliament for Dumbartonshire, where his family possessed some influence; and he was one of those who met at the St Alban’s tavern, to attempt a reconciliation between Fox and Pit and the duke of Portland, with the view of forming what was called "a broad-bottomed administration." This attempt, as is well known, proved unsuccessful. In the following year, as he was cruising down the channel in his ship the Warwick, he encountered the Rotterdam, a Dutch ship of war, bearing fifty guns and three hundred men. The manner in which be attacked this vessel and compelled her to strike—more especially as the engagement happened immediately after the Iris, a ship of equal force, had been baffled in the attempt--gained captain Elphinstone much public notice. Soon after this, he went out to the coast of America, where he served during the remainder of this disastrous war. While on this station, he, in company with other three British vessels of war, captured the French frigate L’Aigle of forty guns, (twenty-four pounders, on the main deck,) and a crew of 600 men, commanded by count de la Touche. Unfortunately for the captors, the enemy’s captain escaped to shore with the greater part of a large quantity of specie which was on board the frigate. Two small casks and two boxes, however, of this valuable commodity fell into the hands of the victors. Along with the captain, there also escaped several officers of high rank, and amongst them the commander-in-chief of the French army in America. During his service on the American coast, captain Elphinstone had the honour to receive on board his ship as midshipman, prince William Henry, afterwards king William IV.; a distinction the more flattering, that the choice of the ship and officer was made by his royal highness himself. At the close of the war, when the subject of our memoir returned to Britain, the prince of Wales appointed him for life to be secretary and chamberlain of the principality of Wales.

In April, 1787, captain Elphinstone married Jane, daughter of William Mercer, Esq. of Aldie, in the county of Perth, a lady of large property, by whom he had a daughter, afterwards viscountess Keith, and wife of count Flahault, aide-du-camp to the emperor Napoleon. In 1786, captain Elphinstone was chosen to represent the shire of Stirling. The breaking out of the French war in 1793, opened a new field for his enterprise and activity, and soon after the occurrence of that event he was appointed to the Robust of seventy-four guns, and sailed under the command of lord Hood to the Mediterranean. The object for which the latter had been sent to these seas was to endeavour to effect a co-operation with the royalists in the south of France. In this his lordship so far succeeded, that the sections of Toulon immediately proclaimed Louis XVII. under a promise of protection from the British fleet, and Marseilles was only prevented from taking a similar step by the approach of a republican army. Before taking possession of Toulon, which was part of the arrangement made with the French by lord Hood, it was deemed proper to secure the forts which commanded the ships in the roads, and for this duty fifteen hundred men were landed under captain Keith, who, after effecting this service, was directed to assume the command of the whole, as governor of fort Malgue. In a few days afterwards general Carteaux appeared, at the head of a detachment of the republican army, on the heights near Toulon. Captain Elphinstone, placing himself at the head of a small body of British and Spanish soldiers, instantly marched out to attack him, and after a gallant contest, completely routed the enemy, and captured his artillery, ammunition, horses, and two stand of colours.

In the October following, captain Elphinstone, with lord Mulgrave and rear-admiral Gravina, at the head of a combined force of British, Spaniards, and Neapolitans, obtained another complete victory over a detachment of the French army, consisting of nearly 2000 men, at the heights of Pharon. In this engagement the enemy’s loss in killed, wounded, and prisoners, was about 1500 men, while on the part of the allied force it amounted only to eight killed, seventy-two wounded, two missing, and forty-eight prisoners.

These successes, however, were insufficient to secure the British in possession of Toulon. The whole force of the republicans became directed to their expulsion; and, finding the place no longer tenable, it was determined, though not without much reluctance, to abandon it. In pursuance of this resolution, the whole of the combined troops, to the number of 8000 men, together with several thousand royalists, were embarked on board the British ships early in the morning of the 8th December, without the loss of a single man. This important service was superintended by captains Elphinstone, Hallinel, and Matthews; and it was principally owing to the care, attention, and vigorous exertions of these officers, and more especially of the first, that it was so well and speedily accomplished. Captain Elphinstone’s efficient services on this and some of the immediately preceding occasions procured him high encomiums from both lord Hood and lieutenant-general Dundas. On his return to England, which was in the year 1794, he was invested with the knighthood of the Bath, having been previously promoted to the rank of rear-admiral of the blue, and in July the same year was made rear-admiral of the white, and in this capacity hoisted his flag on board the Barfleur of ninety-eight guns, and in the year following, having shifted his flag to the Monarch, he sailed with a small squadron for the Cape of Good Hope, then in the possession of the Dutch.

A war being about to commence between Great Britain and the Batavian republic, the object of admiral Elphinstone was to reduce the settlements at the Cape, a service which he effectually accomplished, besides capturing a squadron which had been sent out for its defence. On the completion of this important undertaking he returned to England, now advanced to the rank of vice-admiral; and the cabinet was so highly gratified with the great service he had rendered his country by securing to it so valuable a colony as that of the Cape, that they conferred upon him yet further honours.

In 1797, he was created an Irish peer by the title of baron Keith of Stonehaven-Marischal, and shortly after assumed the command of a detachment of the channel fleet. In this year also, he was presented by the directors of the East India company with a splendid sword, valued at 500 guineas, as an acknowledgment for his eminent services. In 1798, lord Keith hoisted his flag on board the Foudroyant, and sailed for the Mediterranean as second in command under the earl St Vincent, who was already there with a large fleet.

Early in the beginning of the following year, he was promoted to the rank of vice-admiral of the red, and on the occasion of a temporary indisposition of earl St Vincent, assumed the entire command of the fleet. Here he continued employed in blockading the Spanish fleet till May, 1799, when he went in pursuit of the Brest fleet. His search, however, being unsuccessful, he returned to England. In November, he again sailed for the Mediterranean, to take the command of the fleet there, and which was now wholly resigned to him in consequence of the increasing illness of the earl St Vincent. While in this command lord Keith performed a series of important services. By the judicious arrangement of his ships, and the co-operation of lord Nelson, he succeeded in capturing two large French ships proceeding to La Valetta, with troops and stores. He blockaded the ports of Toulon, Marseilles, Nice, and the coast of the Riviera; and, co-operating with the Austrians, who were besieging Genoa, he so effectually cut off all supplies from the French garrison in that place by the activity of his blockade, that they were compelled to surrender. In the following September, the island of Malta was captured by a detachment of his fleet. The British cabinet having determined to make a descent on Spain, lord Keith and Sir Ralph Abercromby entered the bay of Cadiz with a large fleet, having on board about eighteen thousand troops. Circumstances, however, occurred, which the admiral and general conceived warranted them in not attempting the proposed landing, and they accordingly withdrew without making any descent.

The greatest and most brilliant of all lord Keith’s services, however, was yet to be performed; this was the celebrated landing of Aboukir, one of the most splendid affairs in the annals of war; and it was in a great measure owing to the promptitude and skill of the admiral alone, that this critical and perilous enterprise was so triumphantly accomplished. For this important service lord Keith received the thanks of both houses of parliament, and on the 5th December, 1801, he was created a baron of the united kingdom, by the title of baron Keith of Barheath, county of Dumbarton. He had been previously advanced to the rank of admiral of the blue. In the fulness of the country’s gratitude for his services, he was also presented by the corporation of London with the freedom of the city in a gold box, together with a sword of the value of one hundred guineas, and was invested by the Grand Signor with the order of the Crescent, which he had established to perpetuate the memory of the services rendered to the Ottoman empire by the British.

In 1803, lord Keith was appointed commander-in-chief of all his majesty’s ships in the north sea. In 1805, he was further advanced to the rank of rear-admiral of the white, and in 1812, succeeded Sir Charles Cotton as commander-in-chief of the channel fleet. While on this station, it was his lot to be the means of capturing the person of Napoleon Bonaparte, on his flight from France after the battle of Waterloo. The disposition which lord Keith made of his ships on this occasion was such, that the distinguished fugitive, after being taken by captain Maitland of the Bellerophon, acknowledged escape to have been impossible. His treatment of the prisoner was as noble, delicate, and humane, as his arrangements for seizing him had been dexterous. He acted throughout the whole affair with so much good sense and right feeling, that he at once gained the esteem and gratitude of Napoleon, and the approbation of the government which he represented.

In 1814, lord Keith had been created a viscount; and, at the conclusion of the war, by the exile of Napoleon in St Helena, he retired to enjoy his well-earned honours in the bosom of his family, and the society of his former friends. Latterly he resided constantly on his estate of Tulliallan, where he erected a mansion-house suited to his rank and fortune. There he also expended large sums in works of permanent utility, and united with constant acts of voluntary bounty the encouragement of industrious pursuit and useful occupation, those sure sources of comfort to a surrounding population. The strength of his natural understanding enabled him to derive the utmost benefit from all that he had occasion to see or to contemplate. A most tenacious memory and great readiness enabled him to bring all his information effectually into action when the occasion called for it. Such powers, united to a fertility of mind which is rarely excelled, rendered him a most distinguished character in all that regarded his profession. In social intercourse, his kindly nature was constantly predominant: he was entirely free of affectation in conversation, and he dealt out the facts and anecdotes with which his memory was stored, in a most interesting and amusing manner. Lord Keith was invariably influenced by the kindest feelings, for all who were connected with him, and, without solicitation on their part, he was uniformly alive to whatever could promote their interest. But this did not limit the extent of his usefulness to others; on the contrary, being always open to approach, he was zealous in forwarding, to the utmost of his power, the objects of deserving men. Accordingly, it may be safely said of him, that he could reckon as great a number of meritorious officers, of all ranks and descriptions, who had been placed in their proper stations by his efforts, as any man of his rank who served during the same distinguished period of our naval history.