The peace of 1783 having opened the continent to the curiosity of the British traveller, Jackson curtly announced to his friends, that 'he was going to take a walk.' His poverty allowed him no other mode of locomotion; so off he set on the grand tour, carrying with him a map of France, a bundle of clothes, and a scanty supply of money. Crossing the channel, he reached Calais, a place which Horace Walpole, writing from Rome, declared had astonished him more than anything he had elsewhere seen, but in which our adventurer found nothing more astonishing than a superb Swiss regiment. He proceeded to Paris, and thence through Switzerland, by Geneva and Berne, into Germany, at a town of which—Günz in Suabia—he met with a comical enough adventure.
On entering the town he was challenged by a soldier, who, having learned he had no passport, carried him before a magistrate, by whom he was forthwith condemned as a vagabond, and remitted to the custody of a recruiting sergeant. This worthy, in turn, introduced him to the commanding officer, who politely gave our traveller the choice of serving his Imperial and Apostolic Majesty, the Emperor of Germany, either in his cavalry or his infantry forces. But Jackson, strangely insensible to the honour, flatly refused to serve his Majesty in these or any other ways, and desired to be at once set free, and suffered to continue his journey. The officer, doubtless amazed at such presumption, desired the sergeant to convey him to the barracks, where he was placed in a large room, in which were congregated some two hundred or so involuntary recruits like himself—harmless travellers, who, being destitute of passports, the emperor forcibly enlisted into his service. Jackson found his co-mates in misfortune very dirty, very ragged, but perfectly civil and good-tempered. Having a little recovered his serenity—for it is easy to see, though our hero is described as a man of placid demeanour and somewhat Quakerly appearance, he could be not a little fiery at times—he sat down and wrote to the commanding officer, entreating leave to sleep at an inn, and proffering the deposit of all his money as a pledge for his reappearance next morning. The reply was an order that he should surrender his writing materials. At seven o'clock, the appointed sleeping hour, the sergeant returned and gave the signal for bed by rapping with his cane on the floor, which was speedily covered by a number of dirty bags of mouldy straw—the regulation mattresses, it would seem, for involuntary recruits. Jackson—peppery again—refused to lie down, but was at last compelled to do so, and between two of the dirtiest fellows of the lot, each of whom had a leg chained to an arm. The next morning, at his own request, he was brought before the commandant of the town, who had only arrived late the preceding evening, and whom he found seated in his bedroom, 'with all his officers standing round him receiving orders,' says Jackson, 'with more humility than orderly-sergeants.' The commandant repeated the offer of 'cavalry or infantry;' adding that a war was about to commence with the Turks, and that good-behaviour would insure promotion. However, finding Jackson obstinately persistent in his refusal, he quietly observed, in conclusion, that the emperor, as a matter of rule and of right, 'impressed' into his army all such as entered his dominions without certificates of character. 'The order was so tyrannical,' declares our détenu, 'that I could not contain myself. "Put me in chains, if you please," I said, "but I tell you, all Germany shall not make me carry a musket for the emperor."' This impetuous burst of indignation seems to have alarmed the phlegmatic commandant, who accordingly let our adventurer go, counselling him, however, to write to the English ambassador at Vienna for a passport, lest he should get into further trouble.
Jackson passed through the Tyrol into Italy, everywhere indulging his love of scenery and still greater love of adventure; studying with all the acuteness of his countrymen the varied characters of the people he met with, and in his correspondence with home friends, sketching them in language striking for its force, its propriety, and originality. Some of his remarks on men and manners are conceived in a truly Goldsmithian vein, whilst all testify at once to the goodness of his heart and the quickness of his perceptions. At Venice he says that he felt it to be 'such a feast of enjoyment as seldom falls to the lot of man, and never to the lot of any but a poor man, who has nothing conspicuous about him to attract the notice of the crowd,' to possess such facilities as he did for learning what the people of foreign countries really were.
At Albenga, in Piedmont, Jackson arrived one night, tired, hungry, and drenched with rain. Intending to put up at the 'Albergo di San Dominico,' which he had been informed was the best inn, he went by accident to the convent of the same name, and entering, called loudly to be shewn to a private room. 'Instead of telling me I was wrong,' he says, 'the young brethren looked waggish, and began to laugh: when a man is cold and hungry, he can ill brook being the sport of others;' so accordingly—peppery again—he shook his stick angrily at the young monks. And at last one of the most courteous and demure of the number, coming forward, said that although theirs was not exactly a public-house, still the stranger was heartily welcome to walk in, rest, and refresh himself. Discovering his mistake, Jackson of course lost no time in making his bow, his apologies, and acknowledgments.
He returned to England by way of France, having but six sous in his pockets when he reached Bordeaux, where an English merchant, a total stranger, advanced him a few pounds. On the road, he was frequently taken for an Irishman, and not seldom for an Irish priest; under which impression, many civilities were paid him by the simple inhabitants of the country he traversed. Ultimately he landed at Southampton, with just four shillings in his possession; his once black coat having turned a rusty brown, his hat shovel-shaped by ill-usage, and his whole aspect so comical, that the mob hooted him, under the belief that he was a Methodist preacher. Proceeding inland on foot, in the direction of Southampton, he overtook a poor man walking along the road whose looks of unutterable misery induced our traveller to stop and inquire what ailed him. He told Jackson he had a son and daughter dying of a disorder apparently contagious, and that no physician would attend them, as he was too poor to pay the fees. Jackson at once offered his services, which were gratefully accepted. He saw his patients, and prescribed for them, and his heart was touched by their simple expressions of gratitude. 'Their thankfulness,' he says, 'for a thing that would perhaps do them no good, gave me more pleasure than a fee of, I believe, twenty guineas, much in need of it as I was.' The night had gathered in before he reached Winchester, where, at a respectable inn, he partook of such refreshment as his means afforded, and then desired to be shewn to his bedroom. The answer was, that the house contained no bedroom for such as he, and he was finally driven out with the coarsest abuse into the streets. The hour was ten o'clock, the month December, and the severity of the weather may be guessed from the fact, that the snow lay deep on the ground. After wandering about for some time, he at last obtained shelter in a small house in the outskirts of the city. The next day he fared little better. 'On Sunday morning,' he relates, 'I was sixty-four miles from London, and had only one shilling in my pocket. I was hungry, but durst not eat; thirsty, and I durst not drink, for fear of being obliged to lie all night at the side of a hedge in a cold night in December. After dark, I travelled over to Bagshot; was denied admittance into some of the public-houses, ill used in others.' He sought in vain permission even to lie in a barn; but a labourer he fortunately fell in with conducted him to a house, where, at the sacrifice of his last shilling, he secured at length a bed. The next day—foot-sore, penniless, and starving—he entered London. After remaining there a brief space—January 1784—in spite of the inclement season, he set off, again on foot, to Perth—a journey that occupied him three weeks, as he was detained on the way by some friends whom he visited. At Perth, where his old regiment then lay previous to its disbandment, he amused himself by studying Gaelic, and the controversy respecting Ossian and his poems. Quitting Perth, he travelled, still on foot, through the Highlands, the inhabitants of which he was, in the first instance, disposed to class with savages; but when he had observed the originality of conception, the breadth of humour, and the elevated sentiments which mark the Celt, his opinions underwent a total revolution. He was especially delighted with a ragged old reiver or cattle-lifter whom he encountered, and who had given shelter to the Young Chevalier in the braes of Glenmoriston after the battle of Culloden.
On his return to Edinburgh, Jackson married a lady of fortune, the daughter of Dr Stephenson, and niece of his old friend Colonel Francis Shelley, of the 71st regiment; and was enabled by this accession to his means once again to visit Paris, where he not only resumed his medical studies, but acquired the mastery of several languages, Arabic amongst the rest. Having graduated M.D. at Leyden, he came back again to England, and commenced practice at Stockton-upon-Tees, in Durham. Although his reputation speedily became considerable, especially in cases of fever, he seems scarcely to have liked his new avocation. He found solace, however, in his favourite study of languages, which he pursued with unremitting ardour—constantly reading through the Greek and Latin classics, and not only rendering himself familiar with the best works of the modern continental authors, but also with the literature of the Arabic, Persian, Hebrew, and Gaelic tongues. The Bostan of Saadi is said to have been one of his most favourite poems.
On the war breaking out in 1793, Dr Jackson—who, in 1791, had published a valuable work on the fevers of Jamaica and continental America—applied for employment as army-physician; but Mr Hunter, the director-general of the medical department of the army, considering none eligible for such employment who had not served as staffer regimental surgeon, or apothecary to the forces, Jackson agreed to accept, in the first instance, the surgeoncy of the 3d Buffs, on the understanding, that at a future time, he should be nominated physician as he desired. Mr Hunter, however, died soon after this; and his promise was not fulfilled by the Board which succeeded him in the medical direction of the army, and which appears to have pursued Dr Jackson with uniform hostility.
Returning to England with the troops, it was offered to him to accompany, in the capacity of chief medical officer, Sir Ralph Abercromby's expedition against some of the West India islands; and although no employment could possibly have been more agreeable to his taste, he, much to Sir Ralph's chagrin, declined the flattering proposal, on the grounds, that lower terms had been offered to him than to another professional man. Nothing but a sense of professional delicacy, it is plain, governed him in this transaction, for he immediately afterwards embarked (April 1796) as second medical officer in another expedition to San Domingo. During his abode in this island, he was unwearied in enlarging his acquaintance with tropical diseases—observing the rule he had followed in Holland of noting down by the patient's bedside the minutest particulars of every case he attended, the effects of the treatment pursued, and whatever else might shed light on the intricacies of pathological science. He also gave a larger practical operation to the scheme he had years before devised of amending the dietaries of military hospitals.
After the evacuation of San Domingo in 1798, our physician paid a visit to the United States, where he was received with signal distinction, his reputation having preceded him. The latter part of the year found him again at Stockton, publishing a work on contagious and endemic fevers, 'more especially the contagious fever of ships, jails, and hospitals, vulgarly called the yellow-fever of the West Indies;' together with 'an explanation of military discipline and economy, with a scheme for the medical arrangements of armies.' He undertook, about this time, by desire of Count Woronzow, the Russian ambassador, the medical charge of seventeen hundred Russian soldiers, who were stationed in the Channel Islands in a sad state of disease and disorganization; and so admirably did he acquit himself, and so perfect were the hospital provisions he made, that (1800) the commander-in-chief nominated him physician and head of the army-hospital depôt at Chatham—as he says, 'without any application or knowledge on his part.' This appointment was the cause of his subsequent misfortunes.
At Chatham, with the warm approbation of Major-General Hewett, commanding the depôt, he introduced that system of hospital reform which had elsewhere operated so successfully. The changes he effected, as soon as they were made, became known to the Medical Board, and were publicly approved of by one of its members. However, shortly afterwards, an epidemic broke out in the depôt (then removed to the Isle of Wight), arising from the fact, that the barracks were overcrowded with young recruits, but which the Medical Board ascribed to Jackson's innovations, and reported so to the Horse-Guards. The commander-in-chief directed an inquiry to take place before a medical board impannelled for the purpose, and the result of that inquiry may be guessed from a communication made by the War-Office to the commandant of the depôt. This states 'the unanimous opinion of the Board to have exculpated Dr Jackson from all improper treatment of diseases in the sick,' and the commander-in-chief's gratification, 'that an opportunity has thus been given to that most zealous officer of proving his fitness for the important situation in which he is placed.' The result of this wretched intrigue, however, was that Jackson, disgusted with the whole affair, requested to be placed on half-pay, to which request the Duke of York, with marked reluctance, at last (March 1803) acceded.