Mrs Edith Hinkle copied two letters when she visited Ireland back in the 1920/30s: May(??) 26, 1860, from Henry Harbison near Williamsburg, Huntingdon Co.,PA to John Harbison, Moneymore, Co. Derry, Ireland, and Jan 23, 1841: From son Wm Harbison at Vincennes, Knox Co., Indiana; to Wm & Mary Harbison (parents). He had lived in Washington for a time, speaks of brothers John, Francis & Michael.
The second is clearer and more informative. William and Mary Harbison were obviously William b. 1780 and his wife.
John, Francis and Michael were all sons of William. Previously I wondered why there was no William Jr.. Now we know -- he went to America, as his uncles Henry and Sampson did! The most probable American records are an arrival in Philadelphia from Liverpool in 1840; and a death in Philadelphia in 1845. But I'll do more research on this. He was likely in Washington or Knox County Indiana only briefly. William is given as 30 in 1840, which would make him the next sibling (younger, or perhaps older) to my second great grandfather John.
I would dearly like to get hold of these letters. They really should be preserved.