 If it is restricted between the hyperplanes "w" = 0 and "w" = "r" for some nonzero "r", then it may be closed by a 3-ball of radius "r", centered at (0,0,0,"r"), so that it bounds a finite 4-dimensional volume.This volume is given by the formula "r"4, and is the 4-dimensional equivalent of the solid cone.The ball may be thought of as the 'lid' at the base of the 4-dimensional cone's nappe, and the origin becomes its 'apex'.