LITERARY HELP NEEDED

I was a literature buff long before I was a psychometrician and I still remember a fair bit of what I read in that field. One partial memory has been nagging at me recently however and I hope somebody can help me complete it. I remember reading three pieces of advice that an English aristocrat (Chesterfield?) once gave to his son: 1. “Never give your lady one in the morning because you never know what might come up during the day”; 2. “Never hunt South of the Thames”; and 3. ??? If you know any literary buffs please see if they know the third part of the quote. Google doesn’t know the quote at all.

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