The 17-minute colour film is a humorous geography lesson, in which a canoeist travels abruptly through time as he crosses the Great Lakes, experiencing cataclysmic changes in different eras.
At intervals the camera examines surviving evidence of the passage of the Ice Age, such as the striations of the rocks and the folds in the earth of farm landscapes viewed from the air.
He dips his cup for a drink, but with his second sip discovers that the water has been fouled by human-produced industrial waste.
The film proved so popular with children and teachers in test screenings that it was blown up to 35 mm for theatrical distribution.
However, Mason was disappointed when the NFB producer made several changes to his finished work, feeling he had lost creative control.