Formed of alluvial deposits and reclaimed little by little, the flats lying between this inland coastline and the sea are a very fertile tract. They gradually became the seat of a numerous population; and then, owing alike to proximity to the sea and to the number of the navigable waterways, the earliest and most important seat of industry and commerce on the Continent of Europe. The ancient capital of this country, the centre of its trade and the seat of its government when it formed an independent Dukedom, was Ypres. In the eighteenth century was made the discovery that underlying or contiguous to this area was one of the largest of the European coalfields. That discovery changed large parts of the flats by degrees into modern industrial districts. The point to be kept in mind for present purposes is that geographically Flanders is one area, though now situated politically partly in France and partly in Belgium. Its two chief centres of population and industry are Ghent and Lille, both seats of the cotton trade, for like Lancashire in England, this Lancashire of the Continent is engaged mainly in the textile industry and in coal-mining. Lille is close to and in fact situated in one of the larger bays of the inland coastline already spoken of. Nearly midway between Lille and the coast at Dunkirk there is a feature it is important to notice. The otherwise uniform flatness of the country is here broken by a range of low hills shaped like a crescent moon. This range of hills lies to the south of Ypres. From Kleine Zillebeke on the east to the Mont de Cats on the west the ridge is not more than ten miles in length. Ypres is situated within the crescent. The feature is important to notice because of the streams which here take their rise. From the higher level of inland country there flow north-east the Scheldt, and north-west the Somme, and the lower courses of those rivers mark what may be called the natural outer boundaries of this flat area. From the hills south of Ypres again rise the Aa, the Yser, and the Lys. The first two flow outward towards the coast; the Lys bending first round to the south and then to the east, falls into the Scheldt at Ghent.