The Secretary of the Interior, in order to encourage and promote development of production of furs in the Territory of Alaska, is authorized to lease to corporations organized under the laws of the United States, or of any state or Territory thereof, citizens of the United States, or associations of such citizens, public lands of the United States in the Territory of Alaska suitable for fur farming, in areas not exceeding six hundred and forty acres, and for periods not exceeding ten years, upon such terms and conditions as he may by general regulations prescribe: Provided, That where leases are given hereunder for islands or lands within the same, such lease may, in the discretion of the Secretary of the Interior, be for an area not to exceed thirty square miles: Provided further, That nothing herein contained shall prevent the prospecting, locating, development, entering, leasing, or patenting of the mineral resources of any lands so leased under laws applicable thereto: And provided further, That this section shall not be held nor construed to apply to the Pribilof Islands, declared a special reservation by section 646 1

The Secretary of the Interior is authorized to perform any and all acts, and to make such rules and regulations as may be necessary and proper, for the purpose of carrying the provisions of section 687c of this title into effect, including provisions for the forfeiture of any lease for failure to stock the same with fur-bearing animals within a period of one year from the date of the lease, or in the event of the devotion of the lease area primarily to any purpose other than the rearing of such fur-bearing animals.