I saw your message about you 2nd great grandfather Michael Dooling and thought I'd offer the following that may be of help to you. If your Michael Dowling was in fact of Irish descent from the Newcastle area then his real surname in Celtic would have been spelt Dubhlainn prior to about 1800 when it stated to be Anglicised as Doolin, Dooling, Dooley, Dooly, and as the English name Dowling. Dubhlainn is pronounced: "Doo lane" which to the ear of Census takers and those recording passengers names etc was easily misheard as Dooling or Dowling etc, remembering that many of our forebears were not able to read or write they would not have known their name was incorrectly recorded in Baptismal, Marriage, Census or passenger records.
If you have Michael's death certificate it may have his parents names on it, which would help when searching in Ireland. If you haven't already done so try having a look at the internet site: http://www.askaboutireland.ie/griffith-valuation/index.xml
Try the various spellings of the surname Dowling, don't worry about his first name, click on the County field and select Southern Tipperary and Click on Parish and select Newcastle, then click on search. You should find a number of Dowling, Dooling's etc in Newcastle in 1850 the time of the Griffith Valuation, hopefully your 2nd great grandfather or his father will be among them. I hope this helps