Defining the Arms of a Balance
Arm-centers, the pole, and the proportion between spaces and opposed weights
Leonardo sets out definitions for the theory of the balance: the center of each arm's length is the true center of its heaviness, and an arm is the space between an attached weight and the pole. He states the law of the lever in words, that the proportion of the intervals between the arm-centers and the pole equals the proportion of the opposing weights each arm exerts on the other. Three schematic balance beams are drawn across the leaf to illustrate these relations.
On this page
The center of an arm is its true center of heaviness
The center of the length of each balance arm is the true center of its heaviness. An arm of a balance is defined as the space lying between the weight attached to the balance and its pole.
Proportion of arm-spaces equals proportion of opposed weights
Whatever proportion holds between the intervals set between the centers of the arms and the pole of the balance, such is the proportion of the opposing weights that one arm exerts as counterweight on the other by means of its own counterweighing arm.
Arms measured between weight-centers and the pole
The arms of a balance are named as those lying between the centers of the weights attached to it and the pole of that balance. A smaller rod is shown hung from a larger one at the foot of the sheet.