Coulter, Thomas (1793–1843), botanist and medical doctor, was born 28 September 1793 at Carnbeg, a farmhouse north-west of Dundalk, Co. Louth, eldest among four sons and one daughter of Samuel Coulter, gentleman farmer, and his wife Anne (née Dickie). His father's family, of Scottish presbyterian origin, had settled as tenant farmers in the wake of Cromwell (qv). Samuel Coulter had collected a remarkable library of books on exploration, agriculture and bee-keeping, history, religion, and the Irish language. A native Irish-speaker, Samuel possessed a number of significant manuscripts in Irish, some of which he had commissioned from the scribe Patrick Lynch of Loughinisland, Co. Down. After the death of his father (1801) and his mother (1803), Thomas and his siblings were placed under the guardianship of their uncles. A trust fund for their maintenance and education had been set up by their father, and Thomas inherited a freehold estate in the townland of Stumpa and his father's personal estate. The other children also inherited parcels of land. After attending school in Dundalk run by the Rev. William Neilson (qv), a renowned Irish scholar, Thomas entered TCD (1812) under the tutorship of Dr Bartholomew Lloyd (qv), where he studied science subjects, including chemistry, practical mechanics, physiology, entomology, and botany. He received his BA (1817), MA and B.Med. (1820), and later MD (1837). In 1819 he was elected MRIA. While at Trinity he became friendly with astronomer Thomas Romney Robinson (qv), and with Whitley Stokes (qv), and James Townsend Mackay (qv), curator of the college botanic gardens.
Although he graduated in medicine, his overriding interests were botany, fly-fishing, shooting, and catching moths and butterflies. Anxious to pursue his interest in plants and increase his knowledge, he went to work in the Jardin des Plantes, Paris (1821), and the herbarium of Augustin-Pyramus de Candolle (then the leading botanist of Europe) in Geneva (1822). He presented the first taxonomic monograph on the family Dipsacaceae (teasel and scabious) to the Société de Physique de Genève (1823). Dreaming of crossing South America from east to west, he called on the German naturalist and traveller Alexander Humboldt in Paris for advice before returning to London, where he also talked to Joseph Sabine, secretary of the Horticultural Society, about negotiating a collecting expedition for the society. However after a tempting approach by a speculative English mining company, Real del Monte, who had leased mines in Mexico, he accepted their offer to go to Mexico as medical doctor to the miners. No one, including Thomas, seemed disturbed by the fact he had never practised medicine.
He left England in September 1824, reaching the town of Real del Monte, north of Mexico city, in February 1825. Although he participated in some medical duties at the mines, he also assisted Capt. James Vetch, manager of the Mexican operations, with company business, mapping work, and engineering projects. After the mining company acquired an additional mine, the Veta Grande at Zacatecas, Thomas was appointed manager (November 1825). His financial inexperience, and the plummeting of Mexican mine shares in London, contributed to difficulties with the mine. He was transferred to Zimapán to take charge of the Lomo del Toro lead mine, where he was more successful. Throughout this time he collected plants and animal specimens and still dreamed of making a great natural history collection. Specimens included cacti (samples sent back to Geneva and Dublin, 1828), wood samples (with their leaves, flowers, and fruit), snakes, lizards, and insects. In 1829 he left the company after his friend Vetch returned to England. He had long cherished the idea of going to California and of travelling northwards through Alaska, across the Bering Sea to Kamchatka, and overland through Siberia to Europe, for scientific purposes.
The plan was never realised and after a period in Mexico city (1829) and the Sonoran town of Petic, where a prospective business idea failed, he moved to Guaymas (1831) on the Gulf of California. From there he sailed to Monterey, in Alta California. Immediately he set off on a short reconnaissance trip to the southern part of the state: Santa Barbara, San Buenaventura, and on to San Gabriel. The following year (1832) he left for his great journey through southern California. Dissatisfied with his collection and with Alta California, he returned to Mexico. Surviving a revolt in Guanajato (1833), he decided he could not make a decent living in Mexico and that he should return to Ireland. On a visit to London (1835) he was much in demand at soirées, relating his adventures. His collection was eagerly examined, and the great pine cone he brought back from California was described and named Pinus coulteri (Coulter Pine or Big-cone Pine) by David Don at a meeting of the Linnean Society (1835). At the first Irish meeting of the British Association for the Advancement of Science in Dublin (1835), he was feted as a hero. Returning to Ireland, he renewed his friendship with Thomas Romney Robinson.
With his old tutor Lloyd, now provost of TCD, he arranged to use rooms in the college and was promised a position, in return for donating his collection to the college. In 1836 he attended the first evening scientific meeting organised by the RDS, the giant pine cone on display. Lloyd died in 1837, and Thomas's arrangement with Trinity fell through. He did not get on with the new provost, Franc Sadleir (qv), and was asked to leave the college, taking his collections with him. Differences were resolved, however, and by 1840 he moved back to Trinity as curator of the museum on a salary of £100 a year plus chambers (rooms) and commons (meals) (£40). He successfully persuaded the college to fund the purchase of books and collections of shells and insects, and the building of cabinets (altogether £1,600).
However, the demands of his travels over ten years had taken their toll on his health and after an excursion to Wicklow in the rain (April 1843), he caught a fever and never recovered, dying 28 November 1843 in his rooms in Trinity, aged 50. He never married. In his honour the great bell of Trinity was tolled for five days. He was buried in an unmarked grave in Mount Jerome cemetery.
Coulter's legacy to Trinity included bringing together the dispersed natural history collections into one museum and establishing the present herbarium. However, he never proceeded to publish an account of his collections. His niece wrote that ‘he possessed that fatal Coulter indolence and entire want of desire to take advantage of his brilliant abilities’ (quoted in Nelson, 1988). His successor William Harvey (qv) sorted, labelled, and distributed Coulter's botanical specimens and named a few of his discoveries, most notably Romneya coulteri, the matilija or Californian tree poppy (up to 2 m in height), named after Coulter and Thomas Romney Robinson. It first flowered in Ireland about 1870 in the botanic gardens at Glasnevin. His original pine cones and pressed specimens of Californian plants are held in the TCD herbarium. Thomas had inherited his father's library, and after his own death most of it was auctioned off (1844). Robinson, his executor, later sold the Irish manuscripts to the British Museum (1851). A ‘Thomas Coulter memorial garden’ has been developed in the courtyard area of the Dundalk town council museum.