On Jul 18, 12:09*pm, bob wrote:

It is no accident that the high pressure "strong steam" engine was
developed in Cornwall. *

They weren't. Trevithick was from Cornwall, but he had to go to Wales
to find backers for his strong steam work. Cornwall needed single-
acting stationary engines for pumping, so they found the best way to
efficiency (not being constrained by size) was by working at the low
end of the cycle (compounding and condensing) and developing things
like the Woolf and Bull engines.

The last Cornish engine was built in the 20th century, in North Wales
(Dorothea quarry). They certainly weren't made obsolete overnight by
Watt or Trevithick