Agreed, knowledge of how to use an energy source is as important as its presence. The former will not have the opportunity to emerge without the latter, though

Agreed, knowledge of how to use an energy source is as important as its presence. The former will not have the opportunity to emerge without the latter, though the former may be the more proximate cause of a "revolution". (I think it's important to emphasize material inputs because it is a common and very consequential misconception that prosperity is driven by human ingenuity alone.) I didn't know that about coal! Thanks.