He first set to work to make a spiral staircase up the tree, which wound round and round the trunk like the little turret stairs in the tower. Every step was carefully nailed on and properly supported, and the erection grew daily until he had reached four large boughs which branched out twenty feet above the level of the ground. Here he arranged a kind of platform, fixing pieces of wood across in the fashion of a raft, and making a firm railing all round the edge. In the midst of this platform a small hut gradually grew up, the walls of stout hazel-stakes wattled across with branches and willow-withs, while the roof was neatly thatched with reeds. The whole erection was so steady and well made that, though Father, as chief inspector, stamped vigorously about, he could not make it shake, and was able to pass it as perfectly safe, and give his congratulations to the young architect, while even Joe grudgingly admitted that 'Master Forster hadn't made half a bad job of it neither.'