Peer Vries pointed out that Great Britain, after a while, was getting far more labor power from steam engines that it could ever have gotten from coerced labor. In 1840 England had 17 million “steam slaves”: 121 million in 1870, and 411 million in 1896.
Just a little earlier the main power sources were water and wind: watermills and windmills. As late as 1850 water power was “the leading source of mechanical power on both sides of the Atlantic.”
A detailed county-by-county analysis found > 65,000 water-powered mills in the eastern United States by 1840. The distribution looked something like this:
That kind of water wheel usually produced more than 10 horsepower, with 1 horsepower corresponding to the labor effort of about 28 men. So.. in 1840, in terms of raw power, the North had way more chained nixies (> 18 million) than the South had black slaves( ~2.5 million). And when it came to industrial production, it showed.