Sweets are uses of adversity?what?........................t.s.m

In Act 2 Scene 1 of As You Like It, Duke Senor says, "Sweet are the uses of adversity,

Which, like the toad, ugly and venomous,

Wears yet a precious jewel in his head;

And this our life, exempt from public haunt,

Finds tongues in trees, books in the running brooks,

Sermons in stones, and good in every thing.."

The Duke, who has been banished, is expressing how he's maintained a positive worldview despite his suffering. He is saying that he has learned from the "tongues" of the nature he's forced in live in (trees, etc.), and has grown through suffering. The toad comparison has to do with the toad's self-healing capacity. Nature might be cruel, but in that adversity can one still find profit.