That the sum of twenty thousand dollars or so much thereof as may be necessary, is hereby appropriated, out of any money in the treasury not otherwise appropriated, to each of said territories for defraying the expenses of the said conventions, except to Dakota for which the sum of forty thousand dollars is so appropriated, twenty thousand dollars each for South Dakota and North Dakota, and for the payment of the members thereof, under the same rules and regulations and at the same rates as are now provided by law for the payment of the territorial legislatures. Any money hereby appropriated not necessary for such purpose shall be covered into the treasury of the United States.