The glass is aligned to concentrate the sun’s rays, lighting the cannon’s fuse at high noon. More pics here, and a very detailed .pdf from the British Sundial Society on so-called “noon cannons” here. [via Neatorama]
I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.