Dave,

I have seen that diagram in Babcock's book... looks like ripples in a pond.

Geometry is neat, especially such "low-tech" examples as the wheel. I find it fascinating and also somewhat rebellious to think carpenters used no numeric measurements or tape rules, yet built beautifully proportioned buildings. Today carpenters are chained to precise measurements and even need calculators. The wheel suggests that this is all unnecessary. Try selling this to a modern engineer!

In it's simplicity, the wheel also seems deeply mysterious. Why are there 12 arcs, etc.?

And perhaps the deepest question of all, why was it abandoned and forgotten? If it was a pagan symbol, the church would have perhaps killed a carpenter for employing it.