It’s great to see a book related to one of my pet interests made available on Project Gutenberg. Today’s Gem is the classic treatise on light, called (curiously enough) Treatise on Light, by Christiaan Huygens, the Dutch mathematician and physicist who first argued that light propagated as a wave. He has an extensive resumé: according to Wikipedia, he also discovered Saturn’s moon Titan, wrote the first book on probability theory, discovered he the laws governing the motion of pendulums, and patented a pocket watch. He also wrote the book Cosmotheoros, one of the first books to speculate on the possibility of life on other planets.

Good stuff.