The Two Companies respectively may from Time to Time, but only by Agreement, purchase, take on Lease, and otherwise acquire and hold any Lands and Easements or Rights in or affecting Lands which they think requisite for any of the Purposes of this Act, and may purchase, take, and acquire the same on such Terms and Conditions as they think fit: Provided always, that the total Quantity of Land which either of the Two Companies shall at any Time hold shall not exceed Fifty Acres.