The brilliant Bill Hilton covered this topic quite nicely just a few weeks back:
http://www.hiltonpond.org/ThisWeek030701.html
While you are on his wonderful website, think about contributing a few bucks. He makes it really easy - like five different ways to contribute - and he so richly deserves support for the environmental education and scientific research he has been conducting basically on his own dime for so many years!
Ellen Paul
Chevy Chase MD |