"I asked my friend what all that gunk is," I said, pointing at the white foam that coated the surface of the water, "and he said that when we do laundry, and it rinses all the clothes, the soapy water is drained away and put into the river! To which I replied, 'Do we really do that much laundry?'"

I looked at Peter as I spoke and smiled gently, and raised my eyebrows. I wanted to make him laugh, but one has to be careful with clever men. They are so easily bruised.

    He replied, "It's actually caused by manufacturing, usually textiles. They pump and dump millions of gallons in and out of the river every day. That," he nudged the stained soil with his shoe, "is run off." Suddenly, his eyes animated.

"Do you know what heat pollution is?"