The workmen to whom this Act applies are--
         (a) workmen employed in any employment or class of employment which is, or has been declared to be an essential service under rule 126AA of the ¹[Defence of India Rules, 1962 or under rule 119 of the Defence of India Rules, 1971];
         (b) the workmen employed in any factory as defined in clause (m) of section 2 of the Factories Act, 1948 (63 of 1948);
         (c) workmen employed in any mine within the meaning of the Mines Act, 1952 (35 of 1952);
         (d) workmen employed in major port;
         (e) workmen employed in any plantation as defined in clause (f) of section 2 of the Plantations Labour Act, 1951 (69 of 1951);
         (f) workmen employed in any employment specified in this behalf by the Central Government by notification.