In the twentieth century, men toiling in British and American coal mines relied on a primitive alert system for imperceptible dangers: the bright canary bird. Miners toted the caged birds into the depths of the earth to serve as early warnings against poisonous and potentially fatal gas leaks. If the tiny birds suddenly slumped in their cages due to the presence of odorless and colorless carbon monoxide, miners would beat a hasty retreat to safer, cleaner air. Today the expression “canary
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