From A Topographical Dictionary of Ireland, 1837
TAMLAGHT, a parish, partly in the barony of LOUGHINSHOLIN, county of LONDONDERRY, but chiefly in that of DUNGANNON, county of TYRONE, and province of ULSTER, 3 ¼ miles (S. by E.) from Moneymore, on the roads from Toome to Moneymore and from Cookstown to Magherafelt and on the river Ballinderry; containing 2854 inhabitants. The river here forms the southern boundary of the county of Londonderry, and on its south bank, close to its junction with Lough Neagh, stands the village of Coagh, which is described under its own head. According to the Ordnance survey, the parish comprises 4954 ¾ statute acres, 2447 ¾ acres being in the barony of Dungannon, and 2507 in that of Loughinsholin, all fertile land, except about 300 acres of waste and bog: about two-thirds of the surface are arable and the rest meadow and pasture; there is no mountain land.
The inhabitants combine with agriculture the weaving of linen cloth, here carried on to a great extent. There are several quarries of good limestone, much of which is burned for manure. A little westward of the church are seen strata of white limestone, which enter from Seagoe and Maralin, in the county of Down, pass under Lough Neagh, nearly due east and west, and here emerging from their subterranean bed, continue to the neighbourhood of Money-more, and so on to the Magilligan strand. Here were formerly two extensive bleach-greens in full operation, neither of which is now worked. Tamlaght was created a parish in 1783, by Primate Robinson, by separating 6 townlands from the parish of Ballyclog, in the barony of Dungannon, and 5 ½ from that of Ballinderry, in the barony of Loughinsholin: the Primate also built the church and purchased the glebe, with which he endowed it, together with the tithes of the 11 ½ townlands.
The living is a rectory, in the diocese of Armagh, and in the patronage of the Lord-Primate; the tithes amount to £200. The glebe-house was built in 1781, at an expense of £496, of which £92 was a gift from the late Board of First Fruits, the residue having been supplied by the then incumbent. The church is a small plain edifice in the Londonderry portion of the parish. In Coagh is a meeting-house for Presbyterians in connection with the Synod of Ulster, of the second class; within the parish is a meeting-house for those in connection with the Associate Synod; and there are places of worship for Baptists and Wesleyan Methodists, the latter in the market-place of Coagh.
The parochial schools at Tamlaght are supported by the rector, who also contributes to the support of a school at Aghery; and there is a school at Coagh, supported by W. L. Cunningham, Esq.; in these schools are about 280 children. There are also three private schools in which about 90 children are educated; and four Sunday schools.
On the glebe stands a cromlech called Cloughtogel, composed of a stupendous table stone of granite, weighing 22 tons, raised 13 feet above the ground on six uprights of basalt, and under it there is a chamber or vault of considerable extent: there were formerly several other cromlechs connected with this, extending in a line due east and west, the whole surrounded by a circle of upright stones; but, in the process of fencing and other alterations, all have been removed except the first-named. In a field called the "Honey Mug," not far distant, is a large upright pillar of marble of a singular kind, beneath which is an artificial cave: and there are other remarkable stones in the neighbourhood.