A system of naval mathematics : or, practical rules of the art of navigation. ... By J. Bettesworth. - Bettesworth, John. (printed by J. Moore, for the author; and sold by Mr. Le Keux, optician; and the following booksellers, viz. Mr. Wenman, Fleet-Street; Mr. Chappell, Royal - Exchange; Mr. Mottley, Portsmouth; Mr. Gillman, Chatham; and Messrs. Heyden and Son, Plymouth,, 1787)