I thought that "The Riding Lesson" was drawn by Lew Hymers too. Probably from reading the John Moore article years ago.

But Phil Jensen says it was actually drawn by Robert Cole Caples -- see ChipBoard Archive post from 7/13/20:
http://www.thechipboard.com/archives/archives.pl/bid/399/md/read/id/1609528/sbj/lew-hymers-stuff/

Regardless of artist, it's one of my favorite "story" chips of its era.