Section 34. Poles and other structures used to support lines for the transmission of electricity shall be insulated in such manner as to protect employees and other persons from accidents. If such poles and other structures are of any material except wood, and support lines which are operated at a voltage in excess of two thousand volts, they shall be plainly and conspicuously marked ''Dangerous. Keep Away''; provided, that if such poles or structures are used solely to support lines for the transmission of electricity for street lighting and are operated at a voltage of not over ten thousand volts the same need not be so marked if those parts thereof which are accessible to the public are solidly connected to a permanent ground having a resistance of not more than two ohms and if the service wires conducting the current to such poles or structures are placed in underground conduits. The inspector of wires designated or appointed under the authority of section thirty-two, or, in Boston, the fire commissioner, shall enforce this section, and he shall be the sole judge of what constitutes a proper insulation or marking as hereinbefore required. Any owner of poles or other structures, used for the transmission of electricity, shall be punished by a fine of not less than ten nor more than one hundred dollars for each pole or structure left uninsulated, ungrounded or unmarked in violation of this section for an unreasonable time after a request by said inspector or commissioner that the same be properly insulated, grounded or marked as herein required. For the purposes of this section, the words ''inspector of wires'' or ''inspector'' shall, in any town having no such inspector, mean the selectmen.