river Mississippi; thence by a line to be drawn along the middle of the said river Mississippi until it shall intersect the northernmost part of the thirty-first degree of north latitude; south by a line to be drawn due east from the determination of the line last mentioned in the latitude of 31° north of the equator to the middle of the river Apalachicola, or Catahouche; thence along the middle thereof to its junction with the Flint River; thence straight to the head of St. Marys River, and thence down along the middle of St. Marys River to the Atlantic Ocean; east _by a line to be drawn along the middle of the river St. Croix from its mouth in the Bay of Fundy to its source_ and from its source _directly north_ to the aforesaid highlands which divide the rivers that fall into the Atlantic Ocean from those which fall into the river St. Lawrence; comprehending all islands within 20 leagues of any part of the shores of the United States and lying between lines to be drawn due east from the points where the aforesaid boundaries between Nova Scotia on the one part and East Florida on the other shall respectively touch the Bay of Fundy and the Atlantic Ocean, excepting such islands as now are or heretofore have been within the limits of the said Province of Nova Scotia." So far as the present question is concerned, five points of discussion are presented by this article of the treaty of 1783: I. What stream is to be understood by the name of the river St. Croix? II. The determination of the line due north from the source of that river. III. What is the position of the northwest angle of Nova Scotia? IV. The delineation of the line passing through the highlands from that angle to the northwest head of Connecticut River. V. What is to be considered as the northwestern head of Connecticut River? I.--RIVER ST. CROIX.