So Charlie finally figures it out after climbing on the stone work most of the night. From page 318....He reached the window just as the moon came through from the east. The light hit the opposite wall of the Tower and reflected back through the western window then shot out in a clear straight line in the direction of the wall. Charlie quickly measured the angle in relation to the nineth degree angle of the window pane.
"Eighteen degrees," he whispered. "That's the angle." He looked out the window and saw the single moon beam shoot out towards the wall. "Where ever that light ends is the spot."
I spent weeks on this chapter. As I mentioned, on the surface, this is just fun stuff. Our hero solving another mystery that takes him closer to finding the Laws. But if you dig a bit, there are a number of fun things that are hidden here.
Next post I will talk about the Tower in reference to the finding the Laws not from the perspective of mathematics but from the "human spirit."