The other tree he called the month tree. On its stem he was to cut a mark every time his week tree told him a month had passed. But he must be careful, for the months were not of equal length. But he remembered that his teacher had once said in school that the months could be counted on the knuckles and hollows of the hand, in such a way that the long and short months could be found easily and he could tell in this way the number of days in each. Robinson worked at enlarging his shelter a little every day. He was sorely at loss to find something in which to carry the dirt away from the entrance, or enough so that it would not choke up the opening. A large clam shell was all he could think of at present. He would carry the dirt to the entrance and some distance away, and then throw it. Fortunately the ground sloped away rapidly, so that he needed a kind of platform before his door. He was careful to open the cleft at some distance above the large opening. For the air was damp and impure in the shelter. But with the opening made high above, fresh air was constantly passing into, and impure air out of, his cave. Light, too, was admitted in this way. XII ROBINSON MAKES A HUNTING BAG Several days passed with Robinson's hat-making and his calendar-making and his watching the sea. Every day his corn and bananas became more distasteful to him. And he planned a longer journey about the island to see if something new to eat could be found. But he considered that if he went a distance from his cave and found something it would really be of little use to him. "I could eat my fill," he said, "but that is all. And by the time I get back to my cave I will again be hungry. I must find something in which I can gather and carry food." He found nothing. "The people in New York," he said, "have baskets, or pockets, or bags made of coarse cloth. Of them all, I could most easily make the net, perhaps, of vines. But the little things would fall out of the net. I will see whether I can make a net of small meshes." But he soon saw that the vines did not give a smooth surface. He thought for a long while. In his garden at home his father had sometimes bound up the young trees with the soft inner bark of others. He wondered if he could use this. He stripped away the outer bark from the tree, which before had yielded him a fibre for his hat, and pulled off the long, smooth pieces of the inner bark. He twisted them together. Then he thought how he could weave the strands together. He looked at his shirt. A piece was torn off and unravelled. He could see the threads go up and down. He saw that some threads go from left to right (woof), others lengthwise (the warp).