_The American Geographical Society of New York_ _Frontiers of Language and Nationality in Europe, 1917, Pl. I_ THE FRANCO-FLEMISH LINGUISTIC BOUNDARY] The figures of the last (Dec. 31, 1910) Belgian census[13] show that the Flemish provinces are bilingual, whereas the Walloon region is altogether French. Knowledge of French as an educational and business requirement accounts for its occurrence in Flanders. The Romance language, therefore, tends to supersede the Germanic idiom as a national vernacular. The utter absence of Flemish in the Belgian Congo constitutes perhaps the strongest evidence in favor of French as Belgium’s national language. In northwestern France, the language of the plain has, since the thirteenth century, steadily receded before the uplander’s speech. At that time Flemish was spoken as far south as the region between Boulogne and Aire.[14] The area spreading east of the Atlantic, between the present linguistic boundary and a line connecting these two cities, is now bilingual with French predominating. It might be noted here, however, that Boulogne has been a French-speaking city since Frankish days. The use of Flemish in France is restricted to the two arrondissements of Dunkirk and Hazebrouck as well as to a few communes of Lille. Dewachter’s studies[15] in this locality have been summarized by Blanchard.[16] According to these investigations, the arrondissement of Dunkirk contains 41 Flemish-speaking communes, four of purely French language and 20 of dual speech. Of the last, only five reveal a majority of Flemish speakers. In Hazebrouck there are 36 Flemish communes, eight French and nine bilingual. Five of the latter show French predominance. In the arrondissement of Lille, Flemish is spoken only in six bilingual communes, four of which have a majority of French-speaking residents. Furthermore a few Flemish-speaking families are found in the suburbs of St. Omer as well as in a commune near by. About one-third of the inhabitants of Tourcoing understand Flemish. This is also true of one-half the population of Roubaix. In each of the cities of Lille and Armentières, the ratio falls to one-quarter. Outside of the Flemish-tainted communes of the arrondissement of Lille, the boundary of this language is indicated by the course of the Aa, the canal of Neuffossé and the Lys.