I thought I had to research "Sailing" to enable
trade on rivers and coasts? But I had built my capitol one square away from a river - connected the capital to the river by road (one square). Then I settled a city at the coast where the river ended, and somehow I had that 2nd city connected to the tradenetwork without having the technology; "Sailing" nor a road between the 2 cities...
I see that I am not the only one having this "problem": http://forums.civfanatics.com/showthread.php?t=232936
Although I still think its a bug or bad documentation for how it should work...

I see that I am not the only one having this "problem": http://forums.civfanatics.com/showthread.php?t=232936
Although I still think its a bug or bad documentation for how it should work...