LOIR, LA (anc. Liger), the longest river in France, rises at the foot of Gerbier des Jones, among the Cévennes Mountains, in the department of Ardèche, and after a westerly course of 540 miles, falls into the Bay of Biscay. This river drains a district of France nearly equal in extent to one-fourth of the entire kingdom. It becomes navigable at Roanne, and passes the flourishing towns of Orleans, Blois, Tours, Saumur, and Nantes. The navigation is interrupted, however, during four or five months in the year, by frost or floods. To obviate some of the difficulties incidental to the navigation of this river, a lateral canal has been formed along a part of its course, extending from the Canal du Centre to the Canal de Briare. The Loire communicates with the Rhone and Seine by means of canals. The affluents of this river are very numerous and important; many of them navigable. Those on the right are,—the Arroux, the Nièvre, the Maine (formed by the union of the Mayenne and the Sarthe); on the left the Allier, the Loiret, the Cher, the Indre, the Vienne, the Thoué, and the Sevre-Nantaise. To prevent the Loire from spreading over the low grounds along its course, it has been banked in by dykes, built much above its ordinary level. These embankments were never known to give way previous to the great floods of 1846. They gave way at the same place during the fearful inundations of June 1856, carrying away the bridge and village of Savournières, and inundating the communes of La Riche-extra and La Chapelle-aux-Naux, causing a dreadful loss of life and property. The mouth of the river is about 7 miles wide, measured from St Nazaire to Paimbeuf. Ships find great difficulty in taking the mouth of the river, owing to the exposed nature of its position, and to the numerous sandbanks which traverse it.