That it shall be unlawful to use for the burial of the dead any land the drainage from which passes into any stream furnishing the whole or any portion of the water supply of any city, except beyond the distance of one mile from such city: Provided, however, That the prohibitions of this act shall not be enforceable against any land now devoted to burial purposes in which there shall have heretofore been burials and sales of burial lots.
9 P.S. § 10