History: Coal miner and a canary used to warn of dangerous gases underground, England, 1970s [691×540]

https://www.ncm.org.uk/system/uploads/image_content/image/1050/miner_and_canary.jpg via /r/HistoryPorn https://www.reddit.com/r/HistoryPorn/comments/m2yl4a/coal_miner_and_a_canary_used_to_warn_of_dangerous/?utm_source=ifttt