How to find longitude with this shield.
While sailing, longitude may be found in the following manner:

1. Find noon to find midnight.
Using a piece of wood with a straight hole bored in it. This hole would need
to be large enough so that the Vikings could sail as far north as they
wished and the hole would still let daylight pass thru at the noon hour.
This piece of wood needs to be suspended such that the hole is at 90 degrees
to the center of the earth. In other words, the piece of wood needs to be
flat with the surface of the earth. However since we are on a heeling boat,
we can not just lay this piece of wood on the deck. I think suspending it by
three strings would do. Held by a person so as to dampen all rocking motion
on the piece of wood.

Thus to find noon with this hole we need to start counting as soon as any
sun starts to pass thru the hole. Then stop counting when the sun stops
passing thru the hole. Half way between these two times is exactly noon.

Now to use this information to find midnight is as follows. When the sun
starts to shin thru the hole, the man of the watch starts to count EVERY
OTHER SWING of the pendulum. Thus the number of swings counted is exactly
the count from noon to when the sun stops passing thru the hole. Which is
exactly what we want. Now to continue. When the sun stops passing thru the
hole the man on the watch starts to count EVERY SWING of the pendulum. He
continues this count until he reaches his midnight total count.

end quote

This clearly depends on the use of a pendulum to measure time, which is the
problem that prevented anyone from determining longitude until Harrison
invented a clock that was sufficiently accurate and stable, free from
inaccuracy due to ship motion. His invention allowed the British a great
advantage in marine navigation, both Naval and commercial, until others
figured it out too.

Steve

"J T" wrote in message
...
Sun, May 1, 2005, 6:28pm (EDT+4)
(Steven and Gail Peterson) burbled:
The recommended method quickly gets into trouble. A swinging pendulum on
a moving boat, with pitch, roll and yaw accelerations, isn't a reliable
measure of time. See: Longitude : The True Story Lone Genius Who Solved
Greatest Scientific Problem his Time by Dava Sobel.

Hmmm. I would suggest you go back to the link, and reread it very
carefully. Then think about what you read.



JOAT
A highbrow is a person educated beyond his intelligence.
- Brander Matthews