Hi, Cardiff, thanks for your reply.
I know a lot about John David Jones - the Calvinistic Methodist minister. I have found him in all the Censuses from 1871-1901 and have two quite detailed obituaries, which give details of his time at Trevecca and his ministries. I also know a lot about his father, David Jones - I have his marriage certificate and his details in all the 1841 - 1881 Censuses. What I do not know is exactly when David Jones died - although it was probably in 1886 (aged about 51). I have quite a collection of death certificates for David or John Jones (for various reasons he might have used the name John when he lived in Ton) whose deaths were registered in Pontyprydd. But several can be ruled out and three are possible. I would love to know where David Jones and J D Jones lived and worked from 1884-1886 but don't really see how I can discover that. I visited Treorchy Library this summer, and Anthony Pritchard was very helpful - he located the history of Jerusalem Chapel for me. I also looked at the records for Jerusalem Chapel in NLW in Aberystwyth. But none of these can answer my remaining questions, when did David Jones die and where were J D Jones and his father, David Jones working as miners between 1884 and 1886?
I know that J D Jones began to preach in Jerusalem Chapel in 1889, and studied at the Academy in Pontyprydd before he went to Trevecca. Any suggestions about how to answer my remaining questions would be appreciated.

Abersleuth