The frontispiece of Susan Whyman‘s The Pen and the People: English Letter Writers 1660-1800 (OUP 2009), contains an image from the notebook of Gilbert Sorsby Jr with the words:
Gilbert Sorsby/ His Book: 1763.
Sorsby is identified as a Devonshire farmer, but he was only about 13 at the time (see his lifedates in the index of Whyman’s book). The inscription is remarkably similar to that in Harriet Knatchbull’s copy of Lowth’s grammar, and the date is almost identical.
Is the construction typical of eighteenth-century children’s usage? It seems quite likely, for in his grammar Lowth had noted:
‘Thomas’s book:’ that is, ‘Thomasis book;’ not ‘Thomas his book,’ as it is commonly supposed (1762:26).
The Thomas in this quotation was Thomas Henry, Lowth’s son, for whom he had originally written the grammar. Thomas Henry was not yet ten years old when the grammar was published (and much younger when it was first written), so Lowth may well have remembered correcting his son saying Thomas his rather than Thomasis. How old Harriet Knatchbull was when she received Lowth’s grammar as his personal gift to her we don’t know. Quite young, I imagine, as she hadn’t yet mastered the proper abbreviation of the word February (see previous post).