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The 1900 catalogue of Max Kohl of Chemnitz, Germany, lists the left half of this device as Puluj's apparatus for determining the mechanical equivalent of heat. The two small wheels register the number of turns of the rotating conical socket. A corresponding conical piece, almost certainly containing water, was placed into this socket, and was kept from rotating by an arm and spring, thus forming a Proney brake. The semi- circular arm has a scale and reference mark to keep the spring at a constant extension as the system was rotated. This apparatus cost 105 Marks (about $25.00). |