Harvard University’s Putnam Gallery has a collection of historical scientific instruments. Pictured above is Benjamin Martin’s cometarium, which dates back to about 1766. Here’s what it did:
This apparatus was designed to demonstrate how the speed of a comet varies in its orbit according to Kepler’s law of equal areas. The comet Benjamin Martin chose for this instrument is Halley’s Comet, which goes around the Sun every 75 1/2 years. Martin began producing cometaria before Halley’s Comet made its predicted return, and so was betting that Halley would prove correct in his theory.