In his essay on the life and work of Hamilton published in the North British Review, Peter Guthrie Tait claimed that Hamilton's paternal grandfather had come over to Ireland from Scotland, bringing his two sons with him. He also stated that Hamilton's mother was related to `the celebrated Dr. Hutton'.
However Hamilton's first biographer, Robert Perceval Graves, showed that Hamilton's paternal grandfather was established as an apothecary in Dublin long before the birth of his sons, and that other members of the family of the grandfather of William Rowan Hamilton were also settled in Dublin. (Hamilton's paternal grandmother, Grace Hamilton, née Mc Ferrand, was however Scottish.) Graves gave an account of the ancestry of William Rowan Hamilton in the first chapter of his Life of Sir William Rowan Hamilton. He gave further facts, and presented detailed evidence supporting his assertions in the Addendum to the Life of Sir William Rowan Hamilton.
Robert Perceval Graves also stated, in the Addendum to the Life of Sir William Rowan Hamilton, that Sarah Hutton, née Hutton, the mother of William Rowan Hamilton, was not in fact related to the mathematician Dr. Charles Hutton, citing members of the Hutton family then living as his authority. Moreover Hamilton's maternal grandmother was French, her maiden name being Guinant.
David R. Wilkins