At Cato Unbound, there is a set of essays on the
subject in response to Deirdre McCloskey, one of which is by me, others by Greg Clark
and Jonathan Feinstein.
I champion the theory that coal was crucial, because it showed
increasing rather than diminshing returns (the more people mined,
the cheaper it got) and it amplified productivity and commerce. But
there is more to the story than that.