When did Horizon Season 9 Episode 17 air?
Horizon Season 9 Episode 17 aired on May 22, 1972.


Horizon tells amazing science stories, unravels mysteries and reveals worlds you've never seen before.
Horizon investigates the threat to the Snowdonia National Park in Britain, from mining companies.
Direct answers for episode-level questions and details.
Horizon Season 9 Episode 17 aired on May 22, 1972.
This episode runs for approximately 60 minutes.
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