The library was a solid thing of brick and steel and glass and wood, and warm and thick with millions upon millions of books. For two hundred years it had built itself from the blowing dust of the plain, capturing here and there enough mass to frame a window, enough soil to grow a floor. Its long and gently lit corridors, full of musty book smell, grew from long feathered seeds that had spun and whirled in the cold upper atmosphere for untold and uncountable centuries. The books that filled the library were written in letters strange and scattered and unreadable by the slow and torpid reptiles that blinked in the white sunlight; the most intelligent life then upon the planet.
In four hundred years the library had completed itself, and some of the reptiles had discovered the doors that opened inwards for them, but not out again. The library took care of the beasts, fed and watered them, and shifted the books higher on the shelves, out of reach. The reptiles were content but longed instinctively to be outside again. They were a migrant race. The doors opened only inwards, however, the ones the creatures could reach. The library demonstrated again and again other ways, other inaccessible routes out, and the creatures watched, and forgot, and butted foolishly against the low doors again. But the next generation, and the next, and the next, watched, and remembered, and slowly began to consider. The migrant urge pushed them out, and the library drew them back, and a language evolved, and the letters in the books shifted and changed and waited.