I'm not sure the question here. The phrase of a "canary in a coal mine" refers to an early warning of disaster.
Note link added from Wikipedia:
By analogy, the term climate canary is used to refer to a species that is affected by an environmental danger prior to other species, thus serving as an early warning system for the other species with regard to the danger.[3]
Apparently, the phrase "two canaries ..." was used in the film, Inconvenient Truths, in identifying two early warnings of Global Warming.
At one time, canaries were carried into coal mines as an early warning system for the presence of poisonous gases. Since canaries are very small, they would die before humans could be affected.
They were actually 2 canaries that die when the air goes bad alerting human workers to the threat
they are found in mines, they die if they breathe toxic gases and if the canaries die it is time to get out of the mine. (usualy coal mine)
safety
Yes, coal miners mine coal.
to mine coal...
How did they used to coal mine
The Hurriers job was to whear a harnest and pull coal in a coal mine from one part of the coal mine to another.
Coal mine is a found in an ground.
I have not heard of them being used for this. Canaries were however used to detect mine gas in the past.
It is a Miner they go in Mines to mine out coal
The steam engine needs coal, the coal comes from the coal mine