Definitions.
I. A scale is a strait line, whose middle point is immovable, all the rest of its points being at liberty; and that part of the scale, which reaches from the centre to either of the weights, is called the beam.
II. Equiponderation is when the endeavour of one body, which presses one of the beams, resists the endeavour of another body pressing the other beam, so that neither of them is moved; and the bodies, when neither of them is moved, are said to be equally poised.
III. Weight is the aggregate of all the endeavours, by which all the points of that body, which presses the beam, tend downwards in lines parallel to one another; and the body which presses is called the ponderant.
IV. Moment is the power which the ponderant has to move the beam, by reason of a determined situation.
V. The plane of equiponderation is that by which the ponderant is so divided, that the moments on both sides remain equal.
VI. The diameter of equiponderation is the common section of the two planes of equiponderation, and is in the strait line by which the weight is hanged.
VII. The centre of equiponderation is the common point of the two diameters of equiponderation.
SUPPOSITIONS.
Suppositions.