The description and use of a new much-improved sinical quadrant, [electronic resource] : whereby, A Person knowing Addition and Subtraction only, may learn, in Six Hours, to allow for Variation and Lee-Way, &c. Also, determine the Longitude at Sea, and keep a regular Journal of a Voyage to any Part of the World. This Instrument is equally useful in Altimetry, Surveying, &c. for taking Altitudes, and determining right angled Triangles. Invented by John Adams, at the Academy, In Brook-Street, Ratcliff; And Made by Richard Rust, Mathematical-Instrument-Maker, St. Catherine's, London.