Educated at the Meath Hospital, Dublin, and at Guy's Hospital. He began practice as assistant to Dr Wainwright of Liverpool, and after three years was fired with the desire of becoming a medical missionary by the experiences and aspirations of Dr Moffat and John Williams, who had then just returned from their missionary journeys. He was sent out by the London Missionary Society to China in the company of Mr (afterwards Dr) Medhurst, and began his ministration in Macao in 1839. There was at that time only one other medical missionary in China. This was Dr Williams, an American, who had already obtained a footing at Canton. From Macao, Lockhart moved on to Chusan on its first occupation by the British, and in 1843 to Shanghai on its being opened up. Here he founded a hospital, which was so successful from the first that in ten months' time the Chinese patients had numbered 10,000. He remained at this hospital till 1858, and found himself in an isolated position outside the city walls during the Tai-Ping Rebellion, when the hospital lay between the investing army of the Imperialists and the rebels holding Shanghai. The fire of the contending armies poured upon the hospital. Under these trying conditions Lockhart steadily pursued his work among the sick and wounded, the shells on several occasions bursting within the building. The last shell which entered the hospital burst upon the floor of the hall crowded with patients, on the very spot from which only a few moments before a wounded patient had been removed. When the French troops joined the investing forces, Lockhart very courageously volunteered to enter the city in order to try to induce the rebels to surrender and thus avoid more bloodshed. In company with his friend, Mr Wyllie, he safely passed the rebel outposts, and for several hours argued with the leaders, who listened to him but declined his proposals. In the end they burnt the city, which they had evacuated. This great conflagration was always described by Lockhart as the most impressive sight that he had ever witnessed. Leaving the hospital under efficient superintendence he returned to England in 1858. Long before Lockhart's death the institution became the most important hospital for Chinese in China. Lockhart's stay in England was short, but during that time much took place in China. His brother-in-law, Mr (afterwards Sir Harry) Parkes, HM Minister to Japan and China, whilst on a diplomatic mission to the Chinese forces under a flag of truce, had been treacherously taken prisoner with his companions, many of whom died after cruel suffering. As a punishment for this act of treachery Lord Elgin advanced on Peking and destroyed the celebrated Summer Palace, the British Embassy taking up its quarters in the city in October, 1860. Lockhart returned to China with a view to founding a hospital in Peking, which as Medical Officer to the Embassy he was able to do in October, 1861, and during the two and half years of his stay in the capital, over 30,000 patients were treated. Sir Harry Parkes, in a letter to Lockhart, thus expressed the high value he set on his admirable work: "The political good which your proceedings must have will be very great, and your mission will achieve more than the diplomatic in impressing the masses of Peking in our favour. Your hospital I look upon as the most marked incident in our relations with China that has occurred since the signing of the last treaty, and most sincerely do I pray that you may go on and prosper." The Chinese attitude towards Western medicine had for long been not as hostile as is generally imagined. (A work, for instance, on medicine in the Chinese language, at present in the Library of the Royal College of Surgeons, on being taken to the late Sir Richard Douglas at the British Museum was found by him to be a translation of Jenner's early work on vaccination.) Notwithstanding this, however, Lockhart doubtless had to make head against floods of ignorance and superstition in his dealings with the sick Chinese. He returned to England finally in 1864, owing to family circumstances, and settled in practice at 67 Granville Park, Blackheath, Kent, in 1865. Here he remained in uninterrupted devotion to his professional duties till March, 1895. Despite a very busy life he was able to attend regularly the board and committee meetings of the London Missionary Society, where his advice was of the greatest service. He had collected a unique library of works dealing with China, and these he presented to the Society shortly before his death. Subject to certain conditions by him imposed, this is now known as the 'Lockhart Library'. Up to within a few days of his death he was in full vigour and possession of his faculties, but fell very ill on Monday, April 27th, 1896. At a consultation held late at night it was decided that he was too old and feeble to be operated on, although his illness called for immediate surgical intervention. He died, without any suffering, at his residence in Granville Park, on the morning of April 29th, 1896. Mrs Lockhart, whom he married in 1841 and with whom he celebrated his golden wedding, was Miss Catharine Parkes, elder sister of Sir Harry Parkes, and she, together with married sons and daughters, survived him. Publications: *The Medical Missionary in China; a Narrative of Twenty Years' Experience*, 8vo, plate, 2nd ed, London, 1861. *Reports* of Chinese Hospital, Shanghai, and of Chinese Hospital, Peking. Translations from Chinese works on Midwifery, Inoculation, etc, in the *Dublin Med Jour*.