1855, he was elected an elder of the church. He held that office for 61 years, for 53 of which he served as Session Clerk. He was succeeded in that role by his son, James Hay Thin. Thin played an active role in several public and philanthropic bodies. He was at various times the master of the Merchant Company of Edinburgh, a trustee and later chairman of the Edinburgh Savings Bank, president of the Trade Protection Society, director of the Edinburgh City Mission, and director of the Edinburgh Destitute Society. Hymnologist James Thin was also a noted hymnologist. He served on the selection committee of the Presbyterian Hymnal and later of the Church Hymnary. His writings on the subject are quoted extensively in John Julian's A Dictionary of Hymnology. He amassed a vast collection of hymn books and hymnic literature, numbering some 2,500 volumes. The Scotsman described the collection as "perhaps the finest and most complete to be found in the British Islands.". After Thin's death, the collection was donated to the library at New College. Family and personal life In 1849, Thin married Catherine Traquair, with whom he had seven sons. Catherine died in 1869, aged 47. In 1870, he purchased a plot of land in Stow in the Scottish Borders, on which he had a family house built. The house, which was named Ashlea, was completed in 1873. In 1885, at the age of 61, Thin married Elizabeth Darling, a farmer’s daughter. She died in 1905. In later life, Thin lived at 22 Lauder Road in The Grange, Edinburgh, where he died in 1915 aged 91. He is buried in the Grange Cemetery. Thin's eldest son, James Hay Thin (1853–1943), was involved in the family business for most of his working life. Like his father, he was a long-standing elder and Session Clerk of Bristo Church. He was also a director of publishers Oliver and Boyd and Gurney & Jackson. He died in Dollar in 1943 at the age of 90. James Thin's grandson, J. Ainslie Thin (James Hay Thin's eldest son), worked in the business from shortly before World War 1 until the 1950s. In 1917, he was reported missing in action, but was in fact taken prisoner and spent the rest of the war in a German POW camp. His son, James ("Jimmy") Thin (1923–1997), joined the firm in 1949, and along with another family member,