71E. (1) The Government may make rules- ²[* * *]; (b) prescribing the authorities who may declare that the employment of any railway servant or class or the railway servants is essentially intermittent; (c) specifying the railway servants or classes of the railway servants to whom sub-section (2) of section 71D shall apply; (d) prescribing the authorities by whom exemptions under sub-section (3) of section 71C or sub-section (3) of section 71D may be made; (e) providing for the delegation of their powers by the authorities prescribed under clause (d); and (f) providing for any other matter which is to be provided for by rules or which the Government may deem to be requisite for carrying out the purposes of this Chapter. (2) Such rules shall be subject to the provisions of section 143. 71F. Nothing in this Chapter or the rules made thereunder shall authorise the railway servant to leave his duty where due provision has been made for his relief, until he has been relieved.