John Seally was born in Somerset and educated at Hertford College, Oxford (B.A. 1764). He worked as a writer in London, editing the Freeholder's Magazine (1769-70) before teaching school at Bridgwater Square in Westminster. He afterwards entered into orders, and in 1790 was made vicar of East Meon with Froxfield and Steep, in Hampshire.
The accountant's companion; or, schoolmaster's new assistant to practical arithmetic. 1770.
The complete young man's companion: or, an easy introduction to the most useful parts of learning. 1772.
The young lady and gentleman's new guide to the elements of astronomy and geography. 1772.
The penman's delight, or the academical companion. 1775.
The loves of Calisto and Emira; or, the fatal legacy. 1776.
Moral tales, after the eastern manner. 1780?
Belles lettres for the ladies: or, a new and easy introduction to polite literature. 1785?
A complete geographical dictionary, or universal gazetteer. 1787.
The lady's encyclopedia: or, a concise analysis of the belles lettres, the fine arts, and the sciences. 3 vols, 1788.