Pechorin I must have had a different text to you, even though same college and subject, I can't remember exactly what it was, but I know it had some kind of animal in it, because I couldn't remember the word....
and isn't the phrase "le Moyen Age" (although the A in âge should have a circumflex, but I don't know how to do accents on capitals..) so your "average period" is right. unless you used période