But where to go next he could not tell. It was not quite dark: a dull, shineless twilight filled the place. All he knew was that he must go up, and that proved enough for the present, for there he saw the great staircase rising before him. When he reached the top of it, he knew there must be more stairs yet, for he could not be near the top of the tower. Indeed by the situation of the stair, he must be a good way from the tower itself. But those who work well in the depths more easily understand the heights, for indeed in their true nature they are one and the same: mines are in mountains; and Curdie from knowing the ways of the king's mines, and being able to calculate his whereabouts in them, was now able to find his way about the king's house. He knew its outside perfectly, and now his business was to get his notion of the inside right with the outside. So he shut his eyes and made a picture of the outside of it in his mind. Then he came in at the door of the picture, and yet kept the picture before him all the time--for you can do that kind of thing in your mind,--and took every turn of the stair over again, always watching to remember, every time he turned his face, how the tower lay, and then when he came to himself at the top where he stood, he knew exactly where it was, and walked at once in the right direction. On his way, however, he came to another stair, and up that he went of course, watching still at every turn how the tower must lie. At the top of this stair was yet another--they were the stairs up which the princess ran when first, without knowing it, she was on her way to find her great-great-grandmother. At the top of the second stair he could go no farther, and must therefore set out again to find the tower, which, as it rose far above the rest of the house, must have the last of its stairs inside itself. Having watched every turn to the very last, he still knew quite well in what direction he must go to find it, so he left the stair and went down a passage that led, if not exactly towards it, yet nearer it. This passage was rather dark, for it was very long, with only one window at the end, and although there were doors on both sides of it, they were all shut. At the distant window glimmered the chill east, with a few feeble stars in it, and its light was dreary and old, growing brown, and looking as if it were thinking about the day that was just gone. Presently he turned into another passage, which also had a window at the end of it; and in at that window shone all that was left of the sunset, a few ashes, with here and there a little touch of warmth: it was nearly as sad as the east, only there was one difference--it was very plainly thinking of to-morrow. But at present Curdie had nothing to do with to-day or to-morrow; his business was with the bird, and the tower where dwelt the grand old princess to whom it belonged. So he kept on his way, still eastward, and came to yet another passage, which brought him to a door.