Q. I perceive that degrees are to great purpose in Navigation. What is a degree?

• Answer. It is most true that Degrees are of very great employment in Navigation, and a Degree is the 360 part of a Circle, how big or little soever the Circle be, being applied after the several sorts, for the better perfections of the practises Gubernautick, so that there be degrees of Longitude, degrees of Latitude degrees of Azimuth, degrees of Altitude, degrees applied to Measure and degrees applied to Time.

A Degree of Longitude is the 360 part of the Equinoctial.
A Degree of Latitude is the 360 part of the Meridian.
A Degree of Azumuth is the 360 part of the Compass, or Horizon.
A Degree of Altitude is the 90 part of the Vertical Circle, or the 90 part of the distance between the Zenith and the Horizon.

• Every Degree applied to measure doth contain 60 minutes, and every minute 60 seconds, and every second 60 thirds, and every degree of a great Circle so applied containeth 20 leagues, which is 60 miles,
• So by these rates of measure you may prove that a Degree is 20 leagues, or 60 miles, a minute is a mile, and thus much are Degrees and their parts applied to measure.
• Of Degrees applied to Time, there are 15 degrees contained in every hour, so that every degree of Time standeth in the accompt of Time for four minutes, for an hour consisteth of 60 minutes of Time, hath for his fifteenth part 4 minutes, so that a degree being the fifteenth part of an hour, containeth 4 minutes of time so that 15 degrees, or 60 minutes make an hour, 24 hours make a natural day, and 365 days 6 hours are contained in a year: and thus much as touching Time and Degrees applied to Time.

What is the use of Degrees ?

The use of a Degree is to measure between place and place, to find Altitudes, Latitudes, and Lontitudes, to describe Countries, to distinguish Courses, to find the variation of the Compass, to measure time, to find the places and motions of all Celestial Bodies, as the Sun, Moon, Planets, and Stars: To conclude, by Degrees have been performed all Mathematical observations whatsoever, whose use is infinite.