A sling cart, properly speaking, is nothing but a limber, with wheels 7 feet 5.49 inches high, which has a tongue 13 or 16 feet long. It may be considered as a lever of the first kind; so much more advantageous, as the hand of the power applied is longer, and the end which raises the weight shorter. Its fulcrum, which is formed by the united points of the wheels tangent on the earth, may be conceived to be at the lower point of a prop placed under the middle or center of gravity of the axletree; the end which is to raise the weight above the bolster being very near, and the end of the pole, to which the power is applied, very far. The height of its wheels will procure the greatest facility for drawing the weight, provided the pole be made of such length as to make with the supposed prop, or radius of the wheels, an angle nearly ninety degrees.
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