Arnaud,
Some Irish death certificates are available to see free on-line, on the Irishgenealogy site that has Carl Rudolph’s death. However deaths before 1891 are not yet available free.
There are 2 Ellen Felton deaths in the period 1864 to 1901, in Cork, in the irishgenealogy site indexes. If you want the full details you need to send off for a copy of the death certificate.
One was registered Cork, Jan – March 1886. Volume 5, page 170, age at death 45. The other was Cork, Jan – March 1885. Volume 5, page 100. Age 48. The information is very similar in the two entries, and I think it may be the same death recorded in the indexes twice, by mistake. By cross referencing to another source, I think the correct year of death was 1885.
You can order a photocopy of the civil death certificate from GRO Roscommon for €4 (euros).
http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspxYou have to download and print off the form. Then either post or fax it. You can’t e-mail your order to them. However if you want them to e-mail the cert to back to you, they will do that, so tick the relevant box.
I noticed this family in the 1911 census. I suspect it’s connected to your family:
http://www.census.nationalarchives.ie/pages/1911/Cork/Queenstown_No__2_Urban/Ballyvoloon__part_of__Ileen_Terrace_/405715/There’s no list of German migrants to Ireland in the 1860s (or earlier). Immigration procedures then were next to non existent. If Rudolf ever applied for citizenship (and it would have been British Citizenship then as Ireland was not yet a separate nation) there might be a file in the National Archives in London. You could check there. But he was under no obligation to have applied for citizenship. He might just have remained a resident German citizen. There would be no record of that now, so far as I am aware.
I looked to see if Rudolf left a will, but he does not appear to have done so.