Loading your reading…

The Study of Astronomy, adapted to the capacities of youth: In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.Stedman, John, teacher of astronomy

Science

The Study of Astronomy, adapted to the capacities of youth: In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.

Name: The Study of Astronomy, adapted to the capacities of youth: In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.
Author: Stedman, John, teacher of astronomy

Stedman, John, teacher of astronomy

Astronomy -- Juvenile literature -- Early works to 1800

TUTOR. You must consider, that as the earth makes a complete revolution
on its axis in 24 hours, it must pass over 360 degrees in that time:
now, if you divide 360 by 24, the quotient 15, will be the number of
degrees passed over in one hour; 30 degrees will be equal to two hours,
&c. The difference of time between London and his situation is two
hours, consequently the difference of longitude must be 30 degrees: and,
it must be west, because the sun had passed the meridian of London; for,
as the earth revolves from west by south to east, one place which lies
east of another must come first to the meridian or opposite to the sun.
Therefore, when longitude is reckoned from London, if the place lie east
of that meridian the time will be before; if west, after London.

PUPIL. I see it clearly; and as 60 minutes make an hour, if I divide it
by 15, the quotient 4 will be the minutes answering to one degree.

TUTOR. You are right: and for the same reason, 4 seconds of time are
equal to one minute of longitude, which you know is the 60th part of a
degree.—Our captain when arrived at Kingston, finds the difference of
time between it and London 5 ho. 6 min. 32 sec. Can you tell me the
longitude of Kingston?

PUPIL. If I bring the hours and minutes to minutes, and divide by 4, the
quotient I think will be degrees, will it not?

TUTOR. It will: and the seconds of time divided by 4, will be minutes of
longitude. Now try if you can do it.

PUPIL. Five hours 6 minutes, multiplied by 60 will be 306 minutes, this
divided by 4, will give 76 degrees and 2 over, which 2 is half a degree,
or 30 minutes: and 32 seconds of time divided by 4, will be 8 minutes of
longitude, the sum of which is 76 degrees 38 minutes for the longitude
of Kingston.

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.

Public-domain text, read in full here on John Shaqi.

The Study of Astronomy, adapted to the capacities of youth: In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.

No reviews yet