48. If ingress to such place cannot be obtained under section 47 it shall be lawful in any case for a person acting under a warrant and in any case in which a warrant may issue, but cannot be obtained without affording the person to be arrested an opportunity of escape, for a police-officer to enter such place and search therein, and in order to effect an entrance into such place, to break open any outer or inner door or window of any house or place, whether that of the person to be arrested or of any other person, if after notification of his authority and purpose, and demand of admittance duly made, he cannot otherwise obtain admittance: