A letter of advice to all the worthy and ingenuous merchants of the city of London, [electronic resource] : and elsewhere in England, Scotland, and Ireland; And also to all the Worthy and Ingenuous Merchants of France, and of Holland and the United-Provinces, and of Germany, Spain, Portugal, Denmark, and Sweden, and elsewhere in Europe; and To all Ingenuous and Ingenious Artists in Astronomy, Geography, and Navigation; shewing An exact, easie and speedy Way to know the Longitude of all Places in the World, where the European Merchants have their Agents to make Observations; and also How the Longitude of Places may be better known upon Ship-Board. Written by Digby Bull, M. A. and late Rector of Sheldon in Warwick-Shire.