Thanks. I was afraid I was losing it...

I was taught that magnetic variation was due to the difference in magnetic and true north, and that changes with location not the vessel, while magnetic deviation is due to a vessel's own structure and magnetism.

For merchant mariners, Bowditch has always been the "Bible." See Chapter 6: http://www.irbs.com/bowditch/pdf/chapt06.pdf

AFAIK that's correct. The wiki article describes it as "error induced in a compass by local magnetic fields" which would include the hull of the ship (the deviation of which in turn changes with ship's heading).

Then we can talk about navigator's balls

They have a considerable Magnetic declination

Miami Magnetic declination = -5.7 degress West or 5.7 degrees East

Seattle Magnetic declination = 17.2 degrees West

The difference is 22.9 degrees.

To the casual navigator who assumes Mag North and True North (or Grid North with the associated grid convergence compensation) are the same will soon get lost. (A worse situation that being lost is a situation where someone is lost and that person thinks they aren't lost)

A simple 2000 metre bearing directly north (according to the map, assumming that Grid/True North convergence is zero) in the Seatle region will be 591 metres west and 89.4 Metres south from where they think they should be on the map after walking the 2000 metres north following their compass.

This is a quite a good website which explains the differences between Magnetic, True and Grid Norths.
http://www.threelittlemaids.co.uk/magdec/explain.html

Other than quadrantal spheres, the real set of balls usually belong to the guys who have the con in close quarters.

A recently retired pilot I know (I think no one has taken more ships through Hell Gate over the past 30 years) told me that are person who is a pilot needs two things: common sense; and a set of balls. Too little of either can lead to problems. Too much of the latter can also lead to problems.

So ... if one train leaves Seattle at 8:00am local time headed magnetic east going a bazzilion miles per hour, and another train leaves Miami at 11:00am local time headed magnetic west going half of a gazzilion miles per hour ...

When will they meet?

This gives you some sense of how lost I usually felt in school. :-)

"...When will they meet?..."

Not sure. But I know where they will meet. At the scene of the crash. And it will be a dandy...

While I try to understand the declination and deviation concepts, I am primarily a short-distance land navigator who matches compass, GPS, and map to visible physical landmarks. That and looking back at my trail frequently has served me well so far.

At sea out of sight of land, or in deep woods where distant landmarks are not readily visible, for example, I would be in trouble with my current skills. My GPS and use of waypoints and built-in maps would help, but I can only hope I would have time to study-up before encountering the far-at-sea or deep-woods situations.

In any case, once you realize you're lost, the best and most important thing to figure out is where you are, in most cases. Moving before you know where you are can put you into more trouble, on a boat or ship going a short distane in the wrong direction might run you aground. There are circumstances in which one might need to move before knowing where you were, but that should involve needing to get away from something else pretty fast.

> I wonder if a dedicated parent really impressed on their youngster the
> importance of STOPPING the moment they thought they might be lost,
> it would carry over into adulthood?

I think stopping is the key. Sheesh, give people a chance to find you instead of leading them on a merry chase all over thor's creation.

Stop
Think
Observe
Plan