Section 1. Be it enacted, &c., That authority is herein granted to cities of the first class in the State of Pennsylvania, or to any reputable society connected with prison work associated with other benevolent donors, to purchase, alter or erect a suitable building or buildings, to be known as a house or houses of detention for untried juvenile prisoners of both sexes below the age of sixteen years, with convenient capacity for its needs in said cities of the first class.