How did Barrois come to drink the lemonade?

Valentine offered Barrois the lemonade.

“Come, Barrois,” said the young girl, “take some of this lemonade; I see you are coveting a good draught of it.”

“The fact is, mademoiselle,” said Barrois, “I am dying with thirst, and since you are so kind as to offer it me, I cannot say I should at all object to drinking your health in a glass of it.”