Hi
I have been going through my copy of "The Endless Web" the story of John Dickinson & Co paper mills by Joan Evans his great niece but can't find any mention of your Benjamin Harvey.
The first Fourdrinier machine was installed at Frogmore in 1803, & the second at Two Waters in 1806. The engineer was Bryan Donkin who worked for the Fourdrinier brothers. This was all prior to Dickinson taking over the mills at a later date.
According to the book there were 18 paper mills in the county of Herts by 1800, many converted from flour mills.
Do you have any idea were your Benjamin was born, would it have been Hertfordshire.
Maddie