I tried to track this down, found some blogs by the originator, but it only gets more confusing: https://wimflyc.blogspot.com/2021/01/the-henry-adams-curve-clo

I tried to track this down, found some blogs by the originator, but it only gets more confusing: https://wimflyc.blogspot.com/2021/01/the-henry-adams-curve-closer-look.html https://wimflyc.blogspot.com/2021/01/the-henry-adams-curve-c... Henry Adams points out that over 60 years you got 3-4x more power from a ton of coal. That combined with the extra coal dug up, he claims, doubled usable energy every ten years. But then the modern graph simply shows the coal energy, with (as far as I can tell) no attempt to account for the extra efficiency, even though the modern author of the graph makes explicit reference to the increasing efficiency of steam engines.