Industrial Revolution - Coal and Coal Mines
During the Industrial Revolution, the primary source of fuel was coal. It was used for steam engines, locomotives, and to heat buildings (ex. homes, factories). Once coal fields were found, factories were built near-by to ensure that fuel was accessible (and cheap). The coal demand increased significantly due to the advent of railroads.
It was a dangerous (and difficult) job to mine coal. If a tunnel was not sufficiently re-enforced, the miners were prone to cave-ins; thus trapping them inside. Depending on the geographic location (and if there were errors), the mines could flood. It was also possible for gases igniting and causing an explosion. On top of that, many workers faced respiratory diseases such as "black lung."
Due to the difficulties, many people took shortcuts when it came to safety, and this caused many accidents. In the early 1900s, thousands of people were killed in the mines. As a result, the "Bureau of Mines" was created in 1910 to create (and enforce) safety regulations.
Despite of the difficulties/danger, explosives were used to increase productivity. Other improvements came with the steam engines: they pumped water out from the mine, thus allowing the tunnel to be longer (which went along with the usage of explosives - blasting to increase the length of the tunnels).
The formation of these tunnels created new jobs: carpenters and engineers were needed to reinforce the tunnels. Small children (mostly boys) were used to lead donkeys and ponies, who pulled coal through the tunnels.