Actually, John Sewell's son Loyal Chauncey Abbot spelled it with one t. This is per documents and his gravestone in Benton Co., IA. Some of Loyal's children used one t, others used the double t spelling. I have not seen any documentation that proves which way John Sewell spelled his surname. I would be interested to have something that proved it either way. The 1847 Abbott genealogy used the single t as the "correct" spelling. They gave an explanation why that was right. On the other hand, Lemuel Abijah Abbott in his 1906 "Descendants of George Abbottof Rowley Mass."gave a strong arguement for the double t spelling based on English examples.