Resolution of Forces
   This apparatus for demonstrating the resolution of forces is in the collection of Yale University. It was made by Deleuil of Paris, and is described in the 1865 catalogue as "Plan vertical plu le corps parcourt la diagonale d'un carré s'élevant par un movement composé ... 33 francs."

   The black and white picture below shows how the cord is pulled to one side to operate the device. The cord passes across the top of the apparatus to the pulley on the right, and is tied to the pulley in the middle. It then doubles back and passes downward over the middle pulley and connects to the body. Pulling the cord to the left causes the ball to move diagonally upward. 
   A second example of the Resolution of Forces demonstration is on display in the Garland Collection of Classical Physics Apparatus at Vanderbilt University. Unfortunately it has lost its pulley system, making it difficult for the casual observer to identify the apparatus.
   This somewhat similar apparatus is at Bowdoin College in Brunswick, Maine. The cord had become unstrung when I took this picture in the fall of 1979, but it appears that when it is arranged properly, the ball will travel diagonally in the reference frame of the square fixed to the base, and up and down in the sliding frame attached to the pulley directly above the ball.
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