Since this fluid matter, which Descartes calls the .first elem 'nt, is divided into much smaller parts that have much less power to continue their rectilinear motion than do the balls, or the second element, it is clear that this first element must be in the center of the vortex and in the intervals between the parts of the second, and that the parts of the second De arte' believes that tbc.e tiny halls arc solid, hut.