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heh, OccamsTaser, the simplest solution is the one that hurts the most
De Description Temporum is collected in
Selected Literary Essays and
They Asked for a Paper.
Edited to add: Both of those are out of print, but a quick check of my shelves finds the essay is also collected in the book
Essential C. S. Lewis, edited by Lyle Dorsett. It doesn't show up in the table of contents, what is listed there is just 'from
They Asked for a Paper'. That book is still in print, and for a very reasonable price. If you buy a copy, please consider doing so via our bookstore link at the top of the page. We get a few cents of all purchases, which helps defray server costs.