 Similarly, if we vary formula_38 over an interval (a,b) this variation causing formula_42 to have decreased by formula_41, where again formula_37 is a multiple of formula_41 at both formula_54 and formula_55, implies that formula_56 has jumped from formula_46 to formula_45 one more time than it has jumped from formula_45 to formula_46 as formula_38 was varied over the said interval.Thus, formula_62 is formula_41 times the difference between the number of points at which formula_64 jumps from formula_46 to formula_45 and the number of points at which formula_64 jumps from formula_45 to formula_46 as formula_38 ranges over the interval formula_71 provided that at formula_72, formula_73 is defined.In the case where the starting point is on an incongruity (i.e.