SEC. 21. And be it further enacted, That from final decrees in a district court in causes of admiralty and maritime jurisdiction, where the matter in dispute exceeds the sum or value of three hundred dollars, exclusive of costs, an appeal shall be allowed to the next circuit court, to be held in such district. Provided nevertheless, That all such appeals from final decrees as aforesaid, from the district court of Maine, shall be made to the circuit court, next to be holden after each appeal in the district of Massachusetts.