Answer:
Cause: A few experts challenged Champollion's methods
Effect: Defenders of Champollion proved that he was correct
Step-by-step explanation:
Cause and effect is the relationship between events or things in which the different events happen as a result of the other.
So from the excerpt, we are told that a few experts challenged Champollion's methods and clung to the notion that hieroglyphs had a purely symbolic meaning but his (Champollion) defenders proved that his approach was correct beyond every reasonable doubt.
The cause and effect relationship here is such that the accusation that Champollion's methods were false made his followers to perform extra studies and prove that he was correct.