I am sure that I am not the only Civ2 player who has sent a caravan forth on the advice of my Trade Adviser and have it arrive at its destination only to find that they no longer require your cargo. How often does this change? It doesn't take a genius to understand why the game waits until the 1900s to start making Oil a desirable cargo, and even later for Uranium. Does anybody have some insight on this for me?