Bogiephil1: I believe the "French vice" is oral sex
Never heard or read that before!
In certain newspaper "personal ads" soliciting sexual activity, "English lessons" meant spanking or discipline and "French lessons" involved oral sex, presumably blowjobs, since the majority of the practitioners were female. Also, on the "menu" at whorehouses of all levels, "French" was used to refer to a blowjob.
The English/British also used to refer to condoms as "French letters" whereas the French referred to them as "English letters"