"But how?" asked the Doctor.
"By building a bullet proof barricade of poles right here, ten feet in front of our door," answered Jack. "We can easily do it this afternoon and still get some chopping done."
Jack's suggestion was adopted instantly and the boys set to work at once to carry it out. They set up some poles about fifteen feet high and six feet apart, burying their lower ends deep in the earth. Then they set up a second line in the same way about eight inches in front of the first line. Next they placed in the space between the two lines a tier of poles about five inches thick and so closely fitted together as to be bullet proof. Then for complete safety they cut small brush into pieces, and with them filled in what space remained between the two lines of poles.
"Now then," said Jack, "Camp Venture is in a state of defence. But it needs offensive as well as defensive advantages. We are pretty well protected against stray bullets by the wooden barrier we have erected, but we must also be able to shoot over it whenever that becomes necessary. Let's build a platform inside of it, so that one of us standing on it can see everything beyond and shoot as from a breast work, if those fellows insist upon shooting as a condition of the game."
So the boys built the platform of poles, with a little ladder leading up to it, and as it gave a full view of every part of the camp, it was decided that the sentry should thereafter be stationed there in a protected position, instead of being required to expose himself out under the cliff.
CHAPTER XVIII
Parole
During the next week or two after Christmas the boys made notable progress with their chopping, for even the Doctor had by this time become as expert as any of them in wielding an axe, while the other boys, who could scarcely be more expert with that implement than they were at the beginning, acquired a good deal of extra skill in the particular work they were now doing. They more readily recognized the use to which each piece of timber could be put; they acquired new deftness in shaping railroad ties to their destined use, so that the work was done more quickly and with a smaller expenditure of time and force; especially they learned and invented many devices to facilitate their handling of the great bridge timbers, of which they were now sending many down the chute.
All of them except Ed chopped all day. Ed volunteered to take the duty of camp guard upon himself all day every day, so long as his wound should incapacitate him for the hard work of chopping. There was double guard duty to do now of course, for in addition to the guarding of the camp there was the prisoner to watch. But now that the barricade with its platform was built in front of the hut, Ed was confident of his ability to watch both inside and outside, particularly as the wounded man was pretty nearly helpless still, and the boys took all the guns with them when they went chopping, except the one that Ed was using as sentinel. There was still another advantage in the fact that there was now nearly a foot of snow on the ground, and it would have been easy to see a man toiling over its white surface at a great distance.