The disease among the seals got worse. Three more baby seals died, and one was born without a tall. Scientists came from London to look at them, and there were long arti-cles in the newspapers, but no one was sure what the reasons were. Some people said that it was a disease that was always in the water; some people said the seals were eating diseased fish; and some people said that it was the paint factory near the river.

There was a sewage works near the river too. The sewage from another small town came to it. One day, in the factory, John Duncan found two young chemists testing samples of wa-ter from the river. The water came from two kilometres up-stream, near the sewage works.

'Why are you doing that?'he asked, surprised.

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