Grashnak
Chieftain

So, I wanted to play a huge map with 16 nations. All went well for the first hour or so, then I started to meet nation after nation. Being rather well endowed with techs, I decided to trade some for some much needed cash.
Imagine my surprise when, after meeting 10 of the 15 civs out there, that I could only access 4 of them. I pretty quickly realized that you could only see 8 countries at a time on the diplomacy screen, but damned if I can figure out how to access the other 8 countries.

I'm sure it must be possible, but naturally that bit of useful information appears to have slipped by the careful editors of the manual.
HELP!
:enlighten