What does jim learn is Virgil's great hope? Ho does this hope apply also to Gaston Cleric? What line from Virgil (in English) does Jim associate with his old dream about Lena?

Jim spends an enormous amount of time studying Virgil and his concept of patria (loyalty to one's place of origin). Cleric is the man who talks Jim into leaving Lincoln and going to Harvard.

Jim associates the line "Optima dies.... prima fugit," with his old dream about Lena.