Once when she was seventeen he was struck by her prettiness.

It happened at Varvara Petrovna's table.

He began to talk to the young girl, was much pleased with her answers, and ended by offering to give her a serious and comprehensive course of lessons on the history of Russian literature.
Varvara Petrovna approved, and thanked him for his excellent idea, and Dasha was delighted.

Stepan Trofimovitch proceeded to make special preparations for the lectures, and at last they began.

They began with the most ancient period.