Then he must fix the spool on the axis of this great slow wheel, when, turning only as often as the wheel turned, the spool would wind the thread so much the more slowly.
I will not weary my reader with any further detail of Willie's efforts and failures.

It is enough to say that he was at last so entirely successful in timing his machine, for the run of the water was always the same, that he could tell exactly how much thread it would wind in a given time.

Having then measured off the thread with a mark of ink for the first hour, two for the second, and so on, he was able to set his alarum according to the time at which he wished to be woke by the pull at his wrist.
But if any one had happened to go into the garden after the household was asleep, and had come upon the toy water-wheel, working away in starlight or moonlight, how little, even if he had caught sight of the nearly invisible thread, and had discovered that the wheel was winding it up, would he have thought what the tiny machine was about! How little would he have thought that its business was with the infinite! that it was in connection with the window of an eternal world--namely, Willie's soul--from which at a given moment it would lift the curtains, namely, the eyelids, and let the night of the outer world in upon the thought and feeling of the boy! To use a likeness, the wheel was thus ever working to draw up the slide of a _camera obscura_, and let in whatever pictures might be abroad in the dreams of the day, that the watcher within might behold them.
Indeed, one night as he came home from visiting a patient, soon after Willie had at length taught his watchman his duty, Mr Macmichael did come upon the mill, and was just going to turn the water off at the well, which he thought Willie had forgotten to do, when he caught sight of the winding thread--for the moon was full, and the Doctor was sharp-sighted.
"What _can_ this be now ?" he said to himself.

"Some new freak of Willie's, of course.

Yes; the thread goes right up to his window! I dare say if I were to stop and watch I should see something happen in consequence.