The description and use of an instrument, called the double scale of proportion : By which instrument, all questions in arithmetick, geometry, trigonometry, astronomy, geography, navigation, fortification, gunnery, gaging vessels, dialling, may be most accurately and speedily performed, without the assistance of either pen or compasses. By Seth Partridge. - Partridge, Seth, (printed for Hannah Sawbridge at the Bible on Ludgate-Hill,, 1685)