From Arras to the sea near Ostend is a distance of over sixty miles. Nearly the whole of this stretch of country is a dead level. There is a crescent of low heights south of Ypres, but elsewhere, save at and near Cassel, about eighteen miles west of Ypres, there is not a hill worth mention. The hill of Cassel rises suddenly from the plain to a height of 515 feet, and from the summit there is a very extensive view. It is said that thirty-two towns and a hundred villages can be seen from this windmill-studded hill. What is called the Mont des Cats is about the same height as the hill of Cassel. It stands almost on the frontier, to the south-west of Ypres, and was of the greatest importance to the Allies, for it was the key to their position north of the Lys. [Illustration: Brothers in Arms. _Photo, Alfieri._ A British and a French soldier chatting together in Flanders.] I have already told you something of the ancient and beautiful city of Arras.[9] It is the capital of the department of Pas-de-Calais, and stands on the Scarpe, a tributary of the Scheldt. The old province of Artois, of which it was the capital, has changed hands very often during the course of its long and warlike history. It has been successively French, Burgundian, Flemish, Burgundian, German, and Spanish, and it finally came into the possession of France in 1640. You will remember that Arras, the capital, was formerly famous for the tapestry hangings known by its name. The manufacture, however, has long been extinct, and the city has now such varied industries as soap, oil, cast iron, salt, sugar refining, lace making, and the manufacture of agricultural implements. It is also one of the chief grain markets of France. Arras, as you will observe from the map on page 28, stands in a gap in the line of hills which I have mentioned as forming the watershed. Through this gap run the river Scarpe, many roads, and the main railway from Liége by way of Namur, Mons, and Valenciennes to the Channel ports. An enemy striving to push westwards to the English Channel would naturally strive to gain possession of Arras because of its convenient road and railway communications.