In the olden days, miners who went deep into coal shafts used to carry a golden canary with them into the chambers below. The miners, usually people who had spent their entire lives in the depths of mining shafts, were unable to sense when toxic gasses were escaping from the walls. The rule was simple, if you looked over and saw that the canary was laying on its side with "Xs" for eyes, you knew it was time to run as fast as you could towards an elevator.
[Peter M. Denton]
In the olden days, miners who went deep into coal shafts used to carry a golden canary with them into the chambers below. The miners, usually people who had spent their entire lives in the depths of mining shafts, were unable to sense when toxic gasses were escaping from the walls. The rule was simple, if you looked over and saw that the canary was laying on its side with "Xs" for eyes, you knew it was time to run as fast as you could towards an elevator. [Peter M. Denton]