Now it happened that when the war broke out there lay at Barrow three ships of light draught but very strong gun power which had been built for the Brazilian Government. Such ships are known as monitors, after the name of the first of the type, which was built in 1862, during the American Civil War. Really, a monitor is little more than a low, moving gun platform, carrying a little fort, in which one or two heavy weapons are mounted. Each of the three monitors at Barrow displaced 1,200 tons, and carried two 6-inch guns mounted forward in an armoured barbette, two 4.7-inch howitzers aft, and four 3-pounder guns amidships. They were protected by stout armour, and as they drew only four feet seven inches of water, they could move in the shallows where ordinary ships would run aground. These ships were taken over by the British Government at the beginning of the war, and were called the _Humber_, the _Mersey_, and the _Severn_. [Illustration: British Monitors shelling German Trenches. Note the aeroplane and the balloon directing the fire of the monitors' guns.] On the evening of 17th October the three monitors left Dover under the command of Admiral Hood, and arrived off the Flemish coast just as the German attack began. An old cruiser, a battleship, a gunboat, and several destroyers, aided by French warships, also bombarded the coast from outside the shoals. Von Beseler endeavoured to bring his big guns to bear on them, but his artillery was completely outranged, and several of his batteries were destroyed. Every attempt to beat off the monitors failed. The German submarines were ineffective because they could not manoeuvre in shallow water, and their torpedoes, being set to a greater depth than the draught of the monitors, passed harmlessly beneath their hulls. The guns of the monitors swept the coast for six miles inland, their fire, which proved very accurate and deadly, being directed by naval balloons, aeroplanes, and signals from the shore. The Germans could not retaliate; nor could their troops easily protect themselves in trenches, for if they faced the sea they could be enfiladed from the canal, and if they faced the canal they could be enfiladed from the sea. For ten days the big guns of the monitors blazed across the sandhills. One vessel fired a thousand shells in a single day. Heavy batteries were established by the Germans at Ostend on the 24th, but they were at once bombarded, much to the discomfort of the German officers who had taken up their quarters in the big hotels on the sea front. By the end of the month the shore batteries ceased to fire, but before that time the Germans had been forced to give up their attempt to reach Calais by a march along the shore.