On the night of June 6, 1915, the mine tore open the trenches of both sides, and buried one of the British magazines which was filled with hand grenades and killed several British bomb throwers. At about the same moment another supply of British bombs was exploded when it was struck by a shell from a German howitzer. This occurred at a place on the line called Duck's Bill, and resulted in the British being without an adequate supply of hand grenades. The British troops in this action were the soldiers of a British division and a Canadian brigade. The latter included the First Ontario Regiment, the Second and Fourth Canadian Battalions, the Third Toronto Regiment, and the East Yorkshires. The Ontario regiment was directed against a fortified part of the German line which was called Stony Mountain. To the south of Stony Mountain, about 150 yards, was another fortified position called Dorchester. This also was to be taken by the Ontario men. If they succeeded in their work the right flank of the British division would be protected. But it was Stony Mountain that was of most importance to the British. Its machine guns and its northern defenses menaced the route which the British must take to make an advance. In order to prevent the Germans from giving their undivided attention to the Canadians, the British division on the left made an advance against the Teutons north of Stony Mountain. The British artillery had been shelling this part of the German line day and night many days as a preparation for this advance. Its projectiles crashed into the brick fields near La Bassee, and in front of the wrecked village of Quinchy. The German machine-gun crews were hidden behind the brick stacks which were square blocks of burned clay upon which the British shells burst without perceptible effect. The shells that went over the stacks, however, did much damage. Beyond the brick field to the north were the ruins of farm buildings which were also hiding places for the Germans and their machine guns. All the buildings back of the German line had been turned into fortresses whose underground works were concreted and connected with their headquarters by telephone. While the British artillery was attempting to destroy these fortresses it was also hurling lyddite shells into the trenches.