increment

the seminary that furnisheth matter for the formation and increment of animal and vegetable bodies

In the third place, the superelevation and alignment of the track, theoretically calculated for speeds of 70 to 75 m.p.h., was adequate for the 80 to 85 m.p.h. or so normally attained as maxima over the G.N. main line; but nothing whatever had been done to prepare it for the enormous increment over these figures that this run was to produce.