[TheCoelacanth]

Absolutely. Early engines were so inefficient that they could basically only be used in coal mines.

[reverius42]

I'm no expert, but burning coal inside a coal mine sounds like a really bad idea for several reasons.

[TheCoelacanth]

Most aspects of 18th century coal mining probably sound like really bad ideas. It's a notoriously dangerous job.

The engine would also typically be at the top of the mine, not deep inside it.