The Secretary of the Interior is authorized, in his discretion, to acquire by purchase, donation, or otherwise, in behalf of the United States, such lands or interests in lands, easements, and buildings comprising the following: Glass House Point, in James City County; the area known as "The Hook", including the site of the action of October 3, 1781, in Gloucester County; and such additional lands as are desirable for the proper rounding out of the boundaries and for the administrative control of the Colonial National Historical Park: Provided, That the total acreage of lands to be added to the park, with the exception of parkways under the terms hereof shall not exceed seven hundred and fifty acres: Provided further, That the said acquisition of lands or improvements shall be made from such funds as may be appropriated pursuant to the authorization of section 81f of this title.