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Imperial Gazetteer of India, v. 24, p. 26.

26 TRICHINOPOLY DISTRICT from the famous city which is its administrative head-quarters. The word is popularly derived from Trisirappalli, meaning the town of Trisira (`the three-headed'), a rdhshasa, or demon, the brother of Ravana, the villain of the Ramayana, who is said to have ruled the place. The District is bounded on the east by Tanjore, the dividing line for some distance being the Coleroon river; on the north by South Arcot and Salem; on the west by Coimbatore and Madura ; and on the south by the State of Pudukkottai. A small rambling range of hills called the PACHAIMALAIS (`green hills'), which extend into Salem District, lies in the north-western corner; and towards the southern and south-western Physical aspects borders the country is broken up by rocky hills . covered for the most part with scrub jungle. But elsewhere the general character of the District is an undulating plain, divided east and west by the valley of the Cauvery and dotted here and there with small hills, of which the great rock fort in Trichi- nopoly city, the neighbouring Golden Rock near the Central jail, and Ratnagiri near Kulittalai are the principal examples. The CAUVERY is one of the chief natural features of the District. It runs across the centre from west to east, and at the holy island of Srīrangam splits into two branches, of which the one retains the original name of Cauvery and the other is called the Coleroon. These are the most important rivers in the District, and receive the greater part of its drainage. In the north, a small area drains into the VELLAR, which forms the northern boundary for some distance. The eastern half of the more northern of the two portions into which Trichinopoly is divided by the alluvial valley of the Cauvery is occupied by sedimentary deposits; the western by Archaean gneisses and granites, mostly hornblendic. The southern of these two portions is formed of Archaean rocks, granites and gneisses, overlaid in the south-east corner of the Trichinopoly tdluk by a thin bed of con- glomeratic laterite, which has been carved by local denudation into a number of patches forming miniature plateaux. Crystalline limestone occurs in several places north and south of the Cauvery, the prevailing colours being light grey, white, pink (of great beauty), and bluish. Two great and generally rich beds of magnetic iron lie at the southern end of the Pachaimalais. Neither the limestone nor the iron has been worked, though the quantity available is large. The oldest of the sedimentary deposits referred to above are representatives of the Upper Gondwana or Rajmahal system, a formation remarkable for containing great quantities of plant remains of Jurassic age. The so-called 'plant- beds' near Uttattiar in the PerambalCzr tdluk contain numbers of these fossil plants. Their age is considered to be intermediate between the Rajmahal beds proper and the Jubbulpore group of the Indian Jurassic