THE SAND MOTOR.
For slowly moving mechanical displays the following motor is reliable and satisfactory:
A frame of wood (a) is first made, in which is placed a shaft (c) and a wooden pulley (b). The pulley should be tightly secured to the shaft, the end of the latter resting in a step (d) secured to the bottom of the frame. Upon the top of the shaft place a circular board, which holds your display. A cord is run once around your pulley, and then over a small wheel (e) at either side, from whence both ends drop through a hole in the window floor. One end of the cord is weighted, the other connected with a flat weight resting upon the sand, which is your motive power. Make an upright box, as shown in the illustration, with a partition in the middle. In the center of the partition make a small hole for the sand to filter through. The size of the hole regulates the speed of your motor. The box should have a cover for each end. As the sand falls through the hole in the partition the weight which rests upon the sand falls also, your pulley wheel being revolved at the same time. When the sand has run through, which may be in an hour or six hours, as you will arrange, cover the top of the box, reverse it, and place the weight upon the sand again. It is the same principle as the hour glass, and is easily made and operated.
