Today’s Gutenberg Gem is The Project Gutenberg eBook of Scientific American Supplement, May 23, 1891. It includes some nice illustrations of an unusual equatorial telescope, various dogs, moths, and some mathematical illustrations on the conic sections. I’m always on the lookout for illustrations of telescopes, so I thought it was pretty cool. The telescope was a 24″ refractor constructed by Jean Paul Gautier for the Paris Observatory. It was placed in an equatorial elbow arrangement which resulted in a stationary eyepiece. Good stuff, at least if you are a telescope geek like myself.