"About half-a-dozen," Marco replied.
"They haven't answered your fire?"
He had hardly spoken when a hail of bullets pattered on the stone walls. Some had come from the advanced party in the bushes, some from their comrades concealed farther down the track. One flew through the window, and struck the wall a few feet above Enderby's head. The three men drew back.
"It is clear they have discovered where we are firing from," said Burton. "We had better give them the next shots from the roof. There are loopholes in the parapet."
They climbed up the ladder, and, kneeling behind the parapet, peered through the loopholes. For some minutes the enemy continued to fire at the window without exposing themselves. Presently, under cover of their shots, a second party, larger than the first, emerged from the rocks far down the track, and ran up to join their fellows hidden among the bushes. Instantly the three men opened fire; one after another the Bulgars fell, but eight or nine reached shelter in safety. The enemy's fire redoubled in violence; apparently they supposed that the defenders were shooting both from the window and from the roof, for Enderby called up that bullets were flying into the room, and at the same time splinters of stone were struck from the parapet.
Suddenly the firing ceased. Burton, looking through his glasses, saw reinforcements hurrying up along the track far below. Clearly the attack was to be pressed, and the worst was yet to come. So far he was well satisfied. The enemy had been held up for more than an hour; every minute gained might be of priceless service to the British forces. Every now and again the dull boom of artillery from the south told him that his comrades were still fighting a rearguard action against heavy odds. To prevent the enlargement of those odds was worth any sacrifice.
Burton realised that as yet he had had to deal with only a small advanced guard. The fight would take on quite a different complexion when the main body now pressing forward came into action. There was no sign of irresolution in the enemy. Even though he should sweep the track twice or thrice with the machine-gun, they would then discover that his ammunition was expended, and three rifles would avail nothing against the numbers who would pour upwards to the assault. It was time to prepare to play his last card--to light the train which, after an unknown interval, would explode the dynamite and render the track impassable. The tower was doomed. If not carried by assault, it would be shattered as soon as artillery was brought to bear on it. But even though it were destroyed, and all in it, the destruction of the track would delay the enemy for many hours, and his object would be gained.
He inferred, and rightly, as it proved, that the lull would continue until the enemy had come up in sufficient strength to burst through at all costs. But there was no time to spare, especially as so much uncertainty attended the action of the mine. Leaving the two Serbs to keep watch, Burton went below. Nuta was still knotting the lengths of cloth, but he saw at a glance that the coil she had completed would suffice. He made her understand by signs that she was to follow him to the cellar, carrying the revolver.
The eager looks with which the prisoners met him bespoke their confidence that he had come to beg their intercession with victorious Bulgarians. They were immediately undeceived.
"I am going to fire the dynamite," he said. "This place will no longer be safe for you. You must quit the tower. Follow my instructions to the letter. When you leave the entrance, you will cross the enclosure to the wall on the south side, climb it, and go as far along the track southward as you please. If you attempt to move in the opposite direction you will instantly be shot. That is quite clear?"