Conversation so far:
When did the first engines come about?
In 1776, the first engines were installed and working in commercial enterprises.
How did the engines work?
engines were used to power pumps and produced only reciprocating motion to move the pump rods.
Were the engines a success?
The design was commercially successful.
Did they keep making more engines?
for the next five years Watt was very busy installing more engines.
Where were the engines being installed?
mostly in Cornwall.

Question: How did he improve the engines over time?
Self-contained rewrite: How did James Watt improve the engines over time?