Caroline Bartley was my paternal grandmother (& namesake), and I'm also interested in finding out more about our lineage. Over the years I've done some research on the Samoan side from Savaii. Now that I've read the forum postings, I'm beginning to see a possible route for settlement, as various pieces appear to fall plausibly into place.
I'm looking at a publication called _Cyclopedia of Samoa_ (Sydney:McCarron, Stewart & Co., 1907) with brief entries for Charles (p.108) and Alfred (p.89). According to this source, Charles was born in Auckland, NZ in 1857 and moved with his parents to Samoa around 1862. He was a storekeeper and trader in Salano, Savaii. There's mention of his losing two stores and a boat to the massive volcanic eruption, which would corroborate my father's (Ben Gabbard) account about the family business being wiped out by the last big eruption in Samoa. This was the reason they later ended up moving to Upolu and setting up shop in Apia. I believe it was my dad who told me that Chas. had married into the Mapusua aiga in Gautaivai (sp?), Savaii.
Without having the time just now to do a comprehensive search, I'm wondering about the route from Ireland to Samoa. Whether direct to NZ or through the U.S. Given Charles's dates, it seems more likely somehow that it was direct from Ireland to NZ. Otherwise, it would have meant an extraordinary amount of movement for immigrants in the early/mid 19th century. On the other hand, Chas. himself ran away to sea at 10 (!), so there could be some remarkable adventurous traits in these seagoing Bartleys!