The Alexander Acheson line is descended from the Earl of Gosford, and this ancestral line is well documented on the web.Check the Beers, Portrait and Biographical scetches of Washington Co., PA for more information on both lines.See: http://members.aol.com/gracheson/Acheson/achesont.htmhttp://members.aol.com/gracheson/Acheson/achesont.htm
Catherine Clark and John & brother, Mathew Atchison, from Little Britain Twp., Lancaster Co., PA are of a different line in America, but they are undoubtedly related in Scotland or Ireland.With the exception of Cathran, the children of these two Atchisons migrated to Washington Co., PA. John's other three daughters married boys from the Reed family who also went the Wash. Co., PA. With the exception of Matthew, the children changed their spelling to A-C-H-E-S-O-N at this time. Careless spelling was the rule among public officials during this period, and I have found six spelling variants from census takers to store owner's accounts to tax collectors for these families, even for the same person. With very few exceptions (two), the spellings were consistently ACHESON after 1800 in documents signed by the persons themselves in this ancestral line (eg.: deeds). (Check the BLM land grant database for Ohio grants to four Acheson brothers.)
A copy of the probated Will of John Atchison is available from the Lancaster Co., genealogical archives, and the Wills for most of their children are available in Washington Co., PA Willbooks, Volumes I-IV under both spellings.