In 1747, Mr Moore, desirous of adding to the professional knowledge which he had already acquired, by visiting a new and wider field of experience, proceeded to the continent, under the protection of the duke of Argyle, to whom he had procured an introduction. The duke, then a commoner, was lieutenant-colonel of a regiment of foot, and was about to embark for Flanders to serve under the duke of Cumberland, who was there in command of the allied army. On arriving at Maestricht, he attended the military hospitals there, in the capacity of mate, and found abundance of practice, as these receptacles were filled with soldiers, wounded at the battle of Laffeldt, which had just been fought. In consequence of a recommendation which he soon after obtained from Mr Middleton, director-general of the military hospitals, to the earl of Albemarle, Mr Moore removed to Flushing, where he again attended the military hospitals. From this duty, however, he was almost immediately called to the assistance of the surgeon of the Coldstream foot guards, of which regiment his new patron, the earl of Albemarle, was colonel. With this corps, Mr Moore, after passing the autumn of 1747 in Flushing, removed to Breda, where he spent the winter in garrison. In the summer of the following year, a peace having been in the mean time concluded, he returned to England with general Braddock.

Although thus fairly on the world, and in possession of very considerable experience in his profession, Mr Moore was yet only in the seventeenth year of his age. After remaining some time in London, during which he attended the anatomical lectures of his celebrated countryman, Dr Hunter, he went to Paris, to acquire what knowledge might be afforded by an attendance on the hospital and medical lectures of that city, then reckoned the best school in Europe. Fortunately for Mr Moore, his early patron, the earl of Albemarle, was at this time residing in Paris, as ambassador from the court of Great Britain. Mr Moore lost no time in waiting upon his excellency, who, having always entertained the highest opinion of his merits, immediately appointed him surgeon to his household. He had thus an opportunity afforded him of enjoying the first society in Paris, being at all times a welcome guest at the table of the ambassador.

After residing nearly two years in the French capital, Mr Moore was invited by his first master, Dr Gordon, to return to Glasgow, and to enter into partnership with him in his business. With this invitation he thought it advisable to comply, and soon after left Paris. He returned, however, by the way of London, where he remained a few months for the purpose of attending another course of Dr Hunter’s lectures, together with those of Dr Smellie on midwifery. From London he proceeded to Glasgow, when the proposed connexion with Dr Gordon immediately took place. This connexion continued for two years. At the end of that period, his partner having received a diploma, confined himself solely to the practice of physic, while Mr Moore continued the business of a surgeon, assuming now as his partner, Mr Hamilton, professor of anatomy, instead of Dr Gordon, who had necessarily, from the change in his practice, withdrawn from the concern.

In 1769, a circumstance occurred which totally altered Dr Moore’s prospects in life, and opened up others more congenial, there is every reason to believe, than those to which his profession confined him. In the year just named, he was called upon to attend James George, duke of Hamilton, who, then but in the fourteenth year of his age, was affected with a consumptive disorder, of which, after a lingering illness, he died. Dr Moore’s assiduity in this case, although unavailing as to the issue, led to a close connexion with the noble family of his late patient. In the following year, having previously obtained a diploma as doctor of medicine from the university of Glasgow, he was engaged by the duchess of Argyle to attend her son, the duke of Hamilton, as a companion during his travels. The duke, who was at this time about fourteen or fifteen years of age, was, like his brother, also of a sickly constitution, and in Dr Moore was found exactly such a person as was fittest to attend him; one who combined a knowledge of medicine with some experience of continental travel, and an enlightened mind. The young duke and his companion remained abroad for five years, during which they visited France, Italy, Switzerland, and Germany.

On his return from the continent, which was in the year 1778, Dr Moore removed with his family from Glasgow to London, and in the year following, 1779, published his celebrated work, entitled, "A View of Society and Manners in France, Switzerland, and Germany." This work was so well received, that it attained a seventh edition in less than ten years, besides the Irish editions, and French, German, and Italian translations. Two years afterwards, he published a continuation of the same work, entitled, "A View of Society and Manners in Italy." During this period, however, his medical practice was by no means extensive; a circumstance which has been attributed, not to any disinclination on the part of the public, with whom he was so popular as an author, to patronize him, but to his own reluctance to engage in the drudgery entailed on a general practice. The rambling and unfettered life which he had led upon the continent had, in a great degree, unfitted him for the laborious routine of professional duty, and his reluctance again to involve himself in it appears to have adhered to him throughout the whole of his after life, and greatly marred his prosperity in the world.

In 1785, he published his "Medical Sketches;" a work which sufficiently showed that his limited practice did not proceed from any deficiency of knowledge in his profession. It was received with much favour by the public, although it is said to have given offence to some of the medical gentlemen of the time, who thought their interest likely to suffer by the disclosures which it made of what had hitherto been considered amongst the secrets of the profession.

Dr Moore’s next publication was his celebrated novel, "Zeluco," a work unquestionably of the very highest order of merit, and which has long since become one of the fixed and component parts of every British library.

In the August of 1792, he went to Paris, to witness with his own eyes the memorable proceedings which were then in progress in the French capital, and which others were content to learn from report. Dr Moore, on this occasion, frequently attended the National Assembly. He was present also at the attack on the Tuilleries, and witnessed many other sanguinary doings of that frightful period. On his return to England, he began to arrange the materials with which his journey had supplied him, and in 1795, published "A View of the Causes and Progress of the French Revolution," in two volumes 8vo., dedicated to the duke of Devonshire. This work was followed, in 1796, by "Edward: Various Views of Human Nature, taken from Life and Manners, chiefly in England;" and this again, in 1800, by "Mordaunt, being Sketches of Life, Characters, and Manners in various countries; including the Memoirs of a French Lady of Quality," in two volumes 8vo. These works scarcely supported the reputation which their author had previously acquired: in the latter he is supposed, in detailing some gallant feats of a young British officer, to allude to his heroic son, the late general Moore, who was then field-officer.

Dr Moore has the merit of having been one of the first men of note who appreciated and noticed the talents of Burns, who drew up, and forwarded to him, at his request, a sketch of his life. This was followed by a correspondence in 1787, which is to be found in those editions of the poet’s works, which include his Letters.

At the time of the publication of his last work, "Mordaunt," Dr Moore had attained the 70th year of his age. He did not again appear before the public, but spent the short remaining period of his life in the quiet seclusion of his residence at Richmond, in Surrey. After an illness of considerable duration, he died at his house in Clifford Street, London, February 29, 1802.

"As an author," says a distinguished modern writer, [Mr Thomas Campbell, in his memoir of Dr Moore, contributed to Brewster’s Edinburgh Encyclopedia.] "Dr Moore was more distinguished by the range of his information, than by its accuracy, or extent upon any particular subject; and his writings did not owe their celebrity to any great depth or even originality of thought. As a novelist, he showed no extraordinary felicity in the department of invention; no great powers of diversifying his characters, or ease in conducting his narrative. The main quality of his works is that particular species of sardonic wit, with which they are indeed perhaps profusely tinctured, but which frequently confers a grace and poignancy on the general strain of good sense and judicious observation, that pervades the whole of them."