We called attention earlier to how a the equation of the motion of a falling body, is analyzed: the first term of the analysis, dd st a, is translated into language and accordingly into concrete existence to mean that we must suppose a term of a sum (a conception which we have long since abandoned), a term which is a part of the motion, specifically, that it falls on the side of the force of inertia, that is, of absolutely uniform velocity, with the result that in infinitely small parts of time the motion is uniform, but in the finite parts, that is, in those actually existent, it is Cf.