John Vinall's portrait presents a practical man as a polite gentleman of science, a role to which Vinall clearly aspired. Very little is known of his life. He spent most of his career teaching mathematics and writing in Boston and Newburyport, and he is known to have made a map of a portion of Newburyport. In 1794 he sent a copy of his textbook on practical mathematics, The Preceptor's Assistant, or Student's Guide: Being a Systematical Treatise of Arithmetic, both Vulgar and Decimal; Calculated for the use of schools, counting houses, and private families (Boston, 1792) to the American Philosophical Society, through David Rittenhouse, then president of the society. Vinall apologized for writing without introduction to Rittenhouse, for he was "acquainted with the celebrity of your character," but went on to outline his scientific interests, including "observations upon the variations of the magnetic needle" and experiments "in medical electricity." Vinall's links to the world of scientific exchange and correspondence were, in fact, tenuous, but he made the most of every opportunity. John Mason Furness, as little known today as Vinall, painted him in a graceful, informal pose, apparently inscribing a map with his quill pen, his terrestrial globe and drafting instruments close at hand. He is presented as a man of cartographic skill, and the owner of expensive instruments. Such goods defined his identity as clearly as his fierce expression. 
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John Vinall, 1736-1823