The advance of the area of Polish speech, in the form of a tongue of land, to the Baltic coast, is a proof of intimate dependence between Polish nationality and the basin of the Vistula. This northernmost section of the territory in which Polish is spoken, lies entirely within Prussian territory. Centuries of Teutonic influence failed, however, to eradicate completely Slavic language or customs in the valley of the great river. Between Thorn and Danzig, on the left bank of the Vistula, it is estimated that 650,000 Poles are scattered. On the right, the Prussian districts of Lobau, Strassburg and Briesen are centers of intense Polish life and culture. The city of Danzig itself, with a Polish element of only 10 per cent, still gives strong evidence of its Polish institutions. Its monuments are memorials of Poland’s history, and many of its families bear Polish names even though their members use German as a vernacular. Originally a free town, Danzig owes its predominant German population to the inflow of traders of this nationality who have swarmed within its walls since the sixteenth century. The city, standing like a sentinel at the mouth of the Vistula, is in every sense a creation of the river. Traffic from Poland’s innermost districts flows towards the country’s great waterway to be finally landed on the wharves of Danzig. Prior to the partition of Poland, the city was nominally a dependency of that country, but its inhabitants had been granted special trading privileges as well as the right of governing themselves. The city’s commercial relations were highly favored by such a régime and business men from the surrounding country were not slow to realize the exceptional advantages which settlement in the city afforded. By the end of the seventeenth century its population consisted largely of German merchants and their dependents. Frederick II with characteristic far-sightedness realized the extent to which this seaport, together with the river city of Thorn, controlled the traffic between Brandenburg and old Prussia. He did not succeed however in annexing the two cities to his dominions, for it is only since 1815 that they have formed part of Prussian territory. [Illustration: _The American Geographical Society of New York_ _Frontiers of Language and Nationality in Europe, 1917, Pl. IV_ THE AREA OF POLISH SPEECH]