I've read your post with interest and will try to refine some of my information to see if I can make some matches. My Great Grandmother was Margaret BOYLAN (b. Abt 1819) from Tonylion, a small townland that is part of Kilnaleck Town in Crosserlough Parish, County Cavan. I was there five or six years ago. There are a couple of Boylan families to sort out in Kilnaleck and Crosserlough Parish as well as Smith, Brady, Sullivan and so on. However there are good records! Margaret Boylan married Patrick McLoughlin in Rhode Island abt 1855 from where they relocated to Oakville, Ontario where Patrick worked as a shipwright in a shipyard owned by a Scotsman who formed a partnership with Captain Nicholas BOYLEN, (sic), a native of Ireland and former Captain of the schooner Mary Rose that plied the Great Lakes. Capt. Boylan recruited laborers from County Cavan to work in the shipyard. Margaret may have been a cousin to Captain Boylan inasmuch as she had an uncle, Nicholas Boylan, who also emigrated from Cavan to Rhode Island and was in business with his brother Matthew Boylan in Woonsocket. I have access to some old County Cavan records online, so maybe I can help trace your Gaffneys.
Margaret died giving birth to my grandmother, Mary Frances McLoughlin 2/7/1858. She had a sister, Mary Boylan ... and here my memory fades! Due to a computer crash a few years back I will have to look back into my old hard copy documents to sort out the Boylans in my research. Those records are stored in my summer place in New Hampshire. However, there is a also a likely Gaffney connection among cousins from Cavan who came to Woonsocket, Rhode Island in the 19th century assisted by Matthew Boylan and others in the local Irish community. I think the Mary Boylan in my tree may have come over with other family members from Ireland via Nova Scotia and had survived a ship wreck. Again, from misty memory, I think she married Angus McIsaac (?), but I have to go back to sources to straighten out the facts.
Coincidentally, I suspect your Shovlin connections originated from Southwest Donegal where Shovlins and McGills are interrelated with Breslins, McHughs and O'Donnells in the vicinity of Ardara and Killybegs. Shovlins and Breslins settled early in the anthracite coal region in Pennsylvania around Tamaqua, Summit Hill, Mount Carmel, and upwards to Hazelton, Plymouth, Wilkes-Barre and vicinity. Others went to Montana and later branched out where opportunity took them.
I have been over to Ardara and vicinity a few times and hope to go back once more before I become too senile. I may be able to help trace some of your Shovlins back to their original townlands through some of the research I have already done. Also, it might point to some connections I have never been able to verify because in some cases there are several persons about the same age with the same given name and surname. Any detailed information on your Shovlins can be a big help because you sometimes have to know the names of the father and grandfather to establish which branch of the family they identify with. Determining the actual townland where they lived helps determine the family roots. Often nick-names are great identifiers (e.g. "Fiddler Doherty"). For example in the local community, the son of Philip and grandson of Dennis or Daniel would be known as "Joe Phil Den". His brother Daniel might be "Danny Phil Den". Also, the given names Patrick and Peter were often interchangeable and often a nick-name (e.g. "Packy") might help distinguish one from another.
Do you know if your Edward Gaffney was from Cavan? I'll check those records first.
Let me know if I can help trace your Shovlins.