THOMSON, Alexander, jurist, born in Franklin county, Pennsylvania, 12 January, 1788 ; died in Chambersburg, Pennsylvania, 2 August, 1848. He was the son of Archibald Thomson, a soldier in the war of the Revolution. His parents having died when he was a child, he was apprenticed at the age of fifteen to his uncle, Andrew Thomson, a sickle-maker. Meanwhile he found time for private study, and at the end of his apprenticeship had a fair knowledge of Latin and Greek, and English literature. His attainments came under the notice of the Reverend Mr. Grier, father of Justice Robert C. Grief of the United States supreme court, whose family he entered as tutor, at the same time pursuing his own studies. At the end of three years he left Northumberland for Bedford, where he taught, and studied law. After his admission to the bar he rose rapidly in his profession, was elected to the Pennsylvania house of representatives, and afterward chosen to congress to fill a vacancy, serving from December, 1824, till his resignation in May, 1826. During his term he gave much attention to the interests of the District of Columbia, in recognition of which his portrait was placed in the Washington city-hall. After his resignation he was appointed city judge of Lancaster, and soon afterward president-judge of the 16th judicial district, which post he occupied until 1838. Judge Thomson was also professor in the law-school of Marshall college, Lancaster, Pennsylvania --His son, William, surgeon, born in Chambersburg, Pennsylvania, 28 January, 1833, was educated in the Academy of Chambersburg and under private tutors, and was graduated at Jefferson medical college in 1855. Soon afterward he had a lucrative practice at Lower Merion, near Philadelphia, which he relinquished in 1861 in order to enter the regular army as assistant surgeon. He was with the Army of the Potomac throughout the civil war, either in the field or at Washington. For his services after the battle of South Mountain he received the thanks of President Lincoln. He originated two reforms for improving the medical field service: the system of brigade supplies, and the division hospital system. Both these reforms were extended to all the armies by the war department. He was raised to the post of medical inspector of the Department of Washington in 1864, received two brevets, and after the war was sent to Louisiana, but he resigned from the army, 25 February, 1866. Dr. Thomson introduced the local use of carbolic acid as a disinfectant in the treatment of wounds, published an article on the treatment of hospital gangrene by bromine, and was the first, in conjunction with Dr. William F. Norris, successfully to apply the negative process of photography by wet collodion in clinical microscopy. The Army medical museum has been largely indebted to Dr. Thomson for its success, and in its catalogue he is mentioned as the largest contributor both of papers and specimens. Since his retirement from the army Dr. Thomson has practised his profession in Philadelphia. He was elected vice president of the ophthalmological section of the International medical congress that met in Philadelphia in 1876, has lectured at Wills hospital on diseases of the eye for many years, and was elected its emeritus surgeon in 1877. He has been clinical lecturer on diseases of the eye and ear in Jefferson medical college since 1873, and ophthalmic surgeon to the college hospital since 1877. Among his important contributions to medical literature are a series of papers published in the "American Journal of the Medical Sciences," in conjunction with Dr. S. Weir Mitchell, on the use of the ophthalmoscopo in the diagnosis of intracranial tumors, and clinical reports of cases of severe and prolonged headache, dependent upon astigmatism, which have been relieved by the correction of optical defects. He revised the section on diseases and injuries of the eye in Dr. Samuel D. Gross's "System of Surgery," and has invented a new method of diagnosing and correcting ametropia by means of a simple instrument, which is now in general use among ophthalmological surgeons in this country and Europe.--Alexander's youngest son, Frank, railway superintendent, born in Chambersburg, Pennsylvania, 5 July, 1841, was educated at Chambersburg academy, and in 1858 began to learn the railway business in the Pennsylvania railroad company's shops at Altoona. Colonel Thomas A. Scott appointed him to a responsible position in the United States military railway system early in 1861, and he was sent to Alexandria, Virginia, where he assisted in rebuilding bridges and restoring shops, machinery, and rolling stock. On 1 July, 1862, he was transferred to General Don Carlos Buell's army, but, after accompanying it during its march through Kentucky, he returned to the Army of the Potomac. He was then engaged in directing the lines of railroad that played an important part in the Antietam campaign, and was subsequently made assistant superintendent of the lines south of Acquia creek. He co-operated with Colonel Scott in removing the 11th and 12th corps, with their full equipment of artillery and wagons, to Chattanooga, and was afterward given control of the lines south of Nashville, which he rendered capable of transmitting sufficient re-enforcements and supplies to relieve the National army from its embarrassments, and enable it to assume the offensive. He resigned from the military service in 1861, and on 1 June of that year became superintendent of the eastern division of the Philadelphia and Erie railroad. While holding this office he organized a system of track-inspection which was adopted by the entire road, and made improvements in the construction of the roadway. In 1873 he was made superintendent of motive power on the Pennsylvania railroad, and in 1874 became its general manager.