After sorting through all the previous topics on this man (it got so that I would just google "site:rootschat.com reim montreal wales ... " rather than weave through all the interlinking,
well after all that, I see where you are going with this current question, I think:
"If he arrived at Savannah, what boat did he get off and where did it come from, so I can know where to look in Europe for him?" Correct?
I don't think that is the way to go. All roads for him, no matter how they weave, lead back to Wales, from what I can see.
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There is another Pre-Examination of Aliens in Canada record for him that says he arrived in St John's, New Brunswick, in October, 1905:
Michael Reims, 37, butcher and grocer 353 Victoria Ave, Montreal, nationality: Canadian. last residence: 351 Victoria, nearest relative in Canada: wife Elizabeth. destination: Old Orchard, Maine.
born Parydock, South Wales, landed at St Johns New Brunswick, October 1905, brown hair, blue eyes, 5'4 1/2", 128 lbs.
dated January 11, 1921
p 2 going to Old Orchard Beach for season
list of wife and children on page 2.
Wife Elizabeth, Irish, landed New York, September 1904 on the Anchoria, in transit to Canada
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Maybe he travelled back and forth a lot, or maybe he told stories. or both.
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I think you can throw out the "SS Onslow" because I googled and found no reference to it. only the HMS Onslow which was a warship that first sailed in 1916 (if I remember right).
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Canadian arrivals are harder to find than even Savannah. I don't think you will find him there.
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Did passenger ships arrive in Savannah before 1906, when the records are extant? Probably the answer is "of course" but the records are lost or hiding somewhere, or, at best, off line.
Did you ever get the marriage certificate for:
marriage June qtr 1904 Cardiff vol 11a page 584 or page 594 for Micheal Adrian Riim and Hilda Mary Bushen.
Could it be your greatgrandfather, not your grandfather? Legalizing it late in life, or remarrying her or whatever. Do you know when Adrian died, other than before 1 February 1909, when Michael Edward married?
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Why can't that family from Norway be his/yours?