A new set of logarithmic solar tables, calculated and constructed for determining the latitude at sea, By Taking Two Altitudes of the Sun, with the intermediate Time, by a common Watch; and that with Ease and Accuracy, independent of the Sun's meridional Altitude. This most excellent and useful Performance, not only produces the true Latitude at any Time between Nine O'Clock in the Morning, and Three in the Afternoon; but also gives the true Time of the Day, when the greatest Altitude was taken, to twenty Seconds; and if greater Accuracy is required, proportional Parts may be taken. Whence the Sun's Azimuth may be determined by one single Proportion. To which is added, a complete theory, illustrating the rationale of this most useful discovery