Rare Books

Navigation improv'd : being chiefly the method for finding the latitude, at sea as well as by land, by taking any proper altitudes together with the time between the observations : the whole made easy by a new trigonometrical rule : and the means how to refresh the air in the hold of a ship or of a Man of War, and how to measure the number of waves, that pass under a ship during any given time; in order to make a truer estimation of the ship's way : and to have likewise thereby a sort of time-keeper