Answer:
When Jim left Ohio in 1848 there was not a lot of supply for gold in California so there was a lot of demand, but as the amount of supply rose throughout the year the amount of demand decreased leaving people coming later to California gaining less money from the gold then before. As John leaves Ohio in 1849 for the gold in California there is already way too much supply of gold and not that much of demand for this gold. So for John he probably didn't have a great fortune from the gold rush in California. Jim would become a millionaire while John would be left penniless