Speculum nauticum. [electronic resource] = A looking-glass for sea-men. Wherein they may behold, how by a small instrument, called the plain-scale, all nautical questions, and astronomical propositions, are very easily and demonstratively performed / first set forth by John Aspley ... ; whereunto are added many new propositions in navigation and astronomy; and also a third book, shewing a new way of dialling. With an appendix containing the use of all instruments that are used at sea. By H.P. and W.L.