1911 Encyclopædia Britannica/Aar

​AAR, or Aare, the most considerable river which both rises and ends entirely within Switzerland. Its total length (including all bends) from its source to its junction with the Rhine is about 181 m., during which distance it descends 5135 ft., while its ​drainage area is 6804 sq. m. It rises in the great Aar glaciers, in the canton of Bern, and W. of the Grimsel Pass. It runs E. to the Grimsel Hospice, and then N.W. through the Hasli valley, forming on the way the magnificent waterfall of the Handegg (151 ft.), past Guttannen, and pierces the limestone barrier of the Kirchet by a grand gorge, before reaching Meiringen, situated in a plain. A little beyond, near Brienz, the river expands into the lake of Brienz, where it becomes navigable. Near the west end of that lake it receives its first important affluent, the Lutschine (left), and then runs across the swampy plain of the Bödeli, between Interlaken (left) and Unterseen (right), before again expanding in order to form the Lake of Thun. Near the west end of that lake it receives on the left the Kander, which has just before been joined by the Simme; on flowing out of the lake it passes Thun, and then circles the lofty bluff on which the town of Bern is built. It soon changes its north-westerly for a due westerly direction, but after receiving the Saane or Sarine (left) turns N. till near Aarberg its stream is diverted W. by the Hagneck Canal into the Lake of Bienne, from the upper end of which it issues through the Nidau Canal and then runs E. to Büren. Henceforth its course is N.E. for a long distance, past Soleure (below which the Grosse Emme flows in on the right), Aarburg (where it is joined by the Wigger, right), Olten, Aarau, near which is the junction with the Suhr on the right, and Wildegg, where the Hallwiler Aa falls in on the right. A short way beyond, below Brugg, it receives first the Reuss (right), and very shortly afterwards the Limmat or Linth (right). It now turns due N., and soon becomes itself an affluent of the Rhine (left), which it surpasses in volume when they unite at Coblenz, opposite Waldshut.  (W. A. B. C.)