Schoonertrash wrote:

Well . . it was clear to me?????

Massive iron deposis in Canada have nothing at all
to do with compass dip. It's only that the earths
surface is not parallel to the lines of the Earths
magnetic force. Closer to the poles, the magnetism
of the Earth pulls either the north or south pole
of the compass down more. Close to the equator,
the force is almost parallel.

You may be thinking about variation, which is
definitely affected by local magnetic anomalies
like massive iron deposits.

BTW in a couple of "around the world" sailing
books, the skipper/author talks about either
correcting for compass dip or switching compasses.
One of them is 'My Old Man & The Sea' which is a
good read all in itself; but they planned to take
three compasses with them (on a 25' boat no less)
and in the last minute rush, forgot. So they
disassembled their compass and remounted the
magnets to correct for dip. Interesting book, I
gave my father a copy.....

Fresh Breezes- Doug King