Whenever any petition signed by electors of the district equal in number to 15 percent of all votes cast within the district at the last preceding general election of state and county officers is presented to the board asking for the acquisition of public utility works therein named, the clerk shall immediately examine and verify the signatures and certify the result of the examination to the board. If the required number of signatures is found genuine, the clerk shall transmit to the president of the board an authentic copy of the petition, without the signatures thereto.