The sea-mans practice : containing a fundamental probleme in navigation, experimentally verified: namely, touching the compasse of the earth and sea, and the quantity of a degree in our English measure. Also, an exact method or form of keeping a reckoning at sea, in any kinde or manner of sailing. With certain tables and other rules useful in navigation. As also in the plotting and surveying of places. The latitude of the principal places in England. The finding of currents at sea, and what allowance is to be given in respect of them. The fourth edition. By Richard Norwood, reader of the mathematicks.