One Coin That's Not Like The Others

RAY: This week's puzzler is a prelude to next week's puzzler. You are going to learn a mechanism that I hope will help you solve next week's puzzler.

Here it is:

You have eight coins, all of which look, feel and smell identical. One of the coins is heavier than the other seven. You also have a balance scale, on which you can put coins on each side and compare their weights.

TOM: You could obviously do this with four or five weighings.

RAY: But, the question is, how can you take eight coins, and determine which is the bogus, heavier coin, with just two weighings?

Think you know? Drop Ray a note!

[ Car Talk Puzzler ]