A long oar would be the rudder, working it on the starboard side, and there would be a mast; but of course such a craft could only sail before the wind--she could not tack. In shallow water--they could pole along like a punt better than row, for the raft would be cumbrous. Arranging this in his mind, he let the duck burn one side; it had a tendency to burn, as he could not baste it. Soon after he had sat down again he wondered what the time was, and recollected the sundial. This must be made at once, because it must be ready when Charlie made the signal. He looked up at the sun, whose place he could distinguish, because the branches sheltered his eyes from the full glare. The sun seemed very high, and he thought it must be already noon. Giving the duck a twist, he ran to the hut, and fetched a piece of board, his compasses, and a gimlet. Another twist, and then under the teak-tree he drew a circle with the compasses on the board, scratching with the steel point in the wood. With the gimlet he bored two holes aslant to each other, and then ran for two nails and a file. In his haste, having to get back to turn the roast, he did not notice that the matchlock was hung up in the hut. He filed the heads off the nails, and then tapped them into the gimlet holes; they wanted a little bending, and then their points met, forming a gnomon, like putting the two forefingers together. Then he bored two holes through the board, and inserted other nails half through, ready for hammering into the post. The post he cut from one of the poles left from the fence; it was short and thick, and he sharpened it at one end, leaving the top flat as sawn off. Fetching the iron bar, he made a hole in the ground, put the post in, and gave it one tap; then the duck wanted turning again. As he returned to his work he remembered that in the evening the teak and the other trees of the wood cast long shadows towards the hut, which would blot out the time on the sundial. It ought to be put where the full beams would fall on it from sunrise to sunset. The cliff was the very place. He ran up and chose a spot which he could see would be free from shadow, pitched the post, and ran down to the duck. Next he carried up the dial, and nailed it to the top of the post; the two nails kept it from moving if touched, and were much firmer than one. The gnomon at once cast a pointed shadow on that side of the circle opposite the sun, but there were as yet no marks for the hours. He could not stay to look at his work, but went down to the teak, and began to wonder why he did not hear Mark shoot, though very likely in the heat of the day the water-fowl did not cross the open water to the island.