For my friends at Leech Lake...

As reported in Kottke today, this is the "tempest prognosticator," also known as a "leech barometer." It was a 19th century invention used to forecast the weather, based on the principle that leeches apparently become agitated by atmospheric or barometric changes. Twelve leeches were placed in glass pint bottles surrounding a large bell. When an approaching storm disturbs the leech, it wiggles into a tube that triggers a small hammer to strike the bell. The number of leeches ringing the bell would presumably reflect the intensity of the approaching storm. Out of deference to the sensibilities of the leeches, they were placed in a circle to prevent them from feeling to prevent them from feeling "the affliction of solitary confinement." The inventor tested the device in 1850, reportedly with favorable results, but the device inexplicably never found favor with the government or the public. More details and references are available at this Wikipedia link.