- The Sea Compass, is a principal Instrument in Navigation, representing and distinguishing the Horizon, so that the Compass may conveniently be named an Artificial Horizon, because by it are manifested all the limits and divisions of the Horizon, required to the perfecture of Navigation, which directions are 32 points of the Compass, where by the Horizon is divided into 32 equal parts, and every of those points has his proper name, as in the figure following appeareth.
- Also every point of the Compass both contained degrees, minutes, seconds, and Thirds. Which degrees are called degrees of azumuth, whereof there are in every point 11 1/4 so that the whole Compases' Horizon containeth 360 degrees of Azumuth, (for if if you multiply 11 1/4 degrees, the degrees that each point containeth by 32 the points of the compass, it yieldeth 360 - the degrees of the Compass.)
- And of minutes of time each point containeth 45 (being 3/4 of an hour), so that the whole Compass is hereby divided into 24 hours, by which accompt there are in an hour 15 degrees, so that every degree containeth 4 minutes of time, for an hour consisting of 60 minutes hath for his fifteenth part 4 minutes of time, and in every minute there is sixty seconds, and every second contains sixty thirds, either in degrees applies to time or degrees applied to measure: so that the general content of the Compass is 32 points, 360 degrees, and 24 hours with their minutes, seconds and thirds.
What is the use of the 32 Points of the Compass ?
- The use of the 32 points of the Compass, is to direct the skilful Pilote by Horizontal Travers, how he may conclude the Course or Paraboral motion of his Ship, thereby with the greater expedition to recover the place desired.
- Because they divide the Horizon in such limits as are most apt for Navigation, they do also distinguish the Winds by their proper Names, for the Wind receiveth his name by that part of the Horizon from whence it bloweth.
What is the use of 360 degrees of Azumuth ?
- By the degrees of Azumuth is known the quantity of the rising and setting of the Sun, Moon, and Stars, whereby is known the length of the days and nights in all Climates, and at all times;
- They also show a most precise Horizontle delineation of the motion of the Sun, Moon, and Stars, whereby the certainty of time is measured, and the variation of the Compass, with the Poles height, is ingeniously known at all times, and in all places with the help of the Globe.
How is the Hour of the Day known by the Compass ?
- It hath been an ancient custome among Mariners, to divide the Compass into 24 equal parts, or hours, by which they have been used to distinguish time, supposing an East Sun to 6 of the Clock, a Southeast Sun 9 of the clock, and a South Sun 12 of the clock &c. as in the figure above shall plainly appear.
- But this account is very absurd, for with us in England (the Sun having his greatest North declination) it is somewhat past 7 of the Clock at an East Sun, and at a Southeast Sun it is past 10 of the Clock: also when the Sun is in the Equinoctial, the Sun is half the day East, and half the day West, to all those that be under the same: so that the Sun then, and to those people useth but 2 points of the Compass to perform the motion of twelve hours: therefore the definitions of time may not well be given by the Compass, unless the Sun be upon the Meridian, so that you be far toward the North, in such places where the Suns Horizontle motion is very oblique, for there the hour may be given by the Compass without any great error, but else-where it cannot.
- Therefore those that travel must either use the Globe, or an Equinoctial Dial by whom time may be most certainly measured, if there be good consideration of the variation of the Needle by which the Equinoctial Dial is disected, for this is a general thing to be regarded, as well as the Compass, as any Dials, or other Instrument, or conclusion whatsoever wherein the use of the Needle is required, that unless there be good regard unto the variation of the same, there can be no good Conclusion follow of any such practices.