He had left something very important in that room.

What was it?
And had he recovered it?
I begged Madame Bernier who was accustomed to clean the room to look, and she found a pair of eye-glasses--this pair, Monsieur President!" And Rouletabille drew the eye-glasses, of which we know, from his pocket.
"When I saw these eye-glasses," he continued, "I was utterly nonplussed.
I had never seen Larsan wear eye-glasses.

What did they mean?
Suddenly I exclaimed to myself: 'I wonder if he is long-sighted ?' I had never seen Larsan write.

He might, then, be long-sighted.

They would certainly know at the Surete, and also know if the glasses were his.