(1) of section 3 of the Act insofar as relevant for purposes of this case reads as follows: "3. Act not to apply in certain cases (1) The provisions of 803 this Act, except those contained in sections 7, 8, 9, 44, 45 and 46 shall not apply to a) x x (b) any mine engaged in the extrac tion of kankar, murrum, laterite, boulder, gravel, shingle, ordinary sand (excluding moulding sand, glass sand and other mineral sands), ordinary clay (excluding kaolin, china clay, white clay or fire clay), building stone, road metal, earth, fuller 's earth and lime stone: Provided that (i) x x x (ii) where it is an open cast working (a) the depth of the excavation measured from its highest to its lowest point nowhere exceeds six meters; (b) the number of persons employed on any one day does not exceed fifty; and (c) explosives are not used in con nection with the excavation." According to the plain meaning, the exclusionary clause in sub section