Tutor. Very well.—I have just now thought of another method of reducing time to longitude, and longitude to time, which you may probably find easier. However, when you are in possession of both, you may use which you please.
Pupil. That which is easiest must, I think, be best.
Tutor. I will give it you, and let me have your opinion of it.
To reduce time to longitude.
Multiply the hours, minutes, and seconds of time by 15, or rather by the factors as they are called, namely 3 and 5, carrying one for every 60 in the minutes and seconds, and setting down the remainder, thus:
| ho. | min. | sec. | ||
| 5 | 6 | 32 | difference of | |
| 3 | time. | |||
| 15 | 19 | 36 | ||
| 5 | ||||
| Degrees | 76 | 38 | 0 | longitude. |
Divide the degrees and minutes of longitude by 5 and 3 and the quotient will be the difference of time.
Pupil. I give this the preference.
Tutor. As longitude is seldom mentioned without being accompanied with latitude, that you may not be ignorant of its meaning when you meet with it, I shall just tell you that it is the distance of any place from the equator, reckoned in degrees and minutes on the meridian, and is either north or south as the place lies north or south of the equator. The latitude of any place is equal to the elevation of the pole above the horizon. The latitude of the heavenly bodies is reckoned from the ecliptic, and terminates in the arctic and antarctic circles: and their longitude begins at the point Aries.
Pupil. What is the measure of a degree?