Bee -- Highlandman's explaination is a good one. If you have trouble visualizing it, it might help to get something tall and slender, like a candle, and eperiment with a flashlight, so you can see how the shadow moves. First, move the flashlight from right to left from behind the candle, then, move it from left to right, but in front of the candle. You'll see the shadow move in a circle, and turn in opposite directions. I guess the general rule of thumb is: no matter where in the world you are, pay attention to the flow of things, and go in the same direction -- whether it's following shadows around a church, or driving your car in traffic! ;-)

Peter T. -- thanks for the recommendation! Do you remember the title? And why is this book considered the classic?