Chagigah 13: A Select Few

Delving into Ma'aseh Merkavah, when we're not supposed to learn it at all... Who should not be studying Ma'aseh Merkavah? Perhaps everyone, but broad strokes may be acceptable, or acceptable for a select few. Plus, the words of the Torah are not to be taught to a non-Jew. And how R. Elazar defers his opportunities to learn Ma'aseh Merkavah. Also, the purported hiding of the Book of Ezekiel, and the way it was accepted for study - but with some possibly innate danger, nonetheless. Plus the term "chashmal."