Section 3I(4)(a) in Tamil Nadu District Municipalities Act, 1920
(a)The offices of the chair-persons of the [Third Grade Municipality] [Substituted for the word 'Town Panchayat' by the Tamil Nadu District Municipalities (Amendment) Act, 2004 (Tamil Nadu Act 24 of 2004)] shall be reserved for the persons belonging to the Scheduled Castes and the Schedule Tribes and the number of offices so reserved shall bear, as nearly as may be, the same proportion to the total number of offices in the State as the population of the Scheduled Castes in all the [Third Grade Municipality] [Substituted for the word 'Town Panchayat' by the Tamil Nadu District Municipalities (Amendment) Act, 2004 (Tamil Nadu Act 24 of 2004)] in the State or the Scheduled Tribes in all the [Third Grade Municipality] [Substituted for the word 'Town Panchayat' by the Tamil Nadu District Municipalities (Amendment) Act, 2004 (Tamil Nadu Act 24 of 2004)] in the State, bears to the total population of all the [Third Grade Municipality] [Substituted for the word 'Town Panchayat' by the Tamil Nadu District Municipalities (Amendment) Act, 2004 (Tamil Nadu Act 24 of 2004)] in the State.