BB’ IS EQUAL TO HALF OF BC, I.E. ONE HOUR OF WORK. IF NOW IN AC POINT B IS MOVED BACK TO B’, THE OVERWORK BECOMES B’C, IT INCREASES BY HALF, FROM TWO TO THREE HOURS, ALTHOUGH THE WHOLE DAY STILL COUNTS ONLY TWELVE HOURS. THIS EXTENSION OF THE EXCESS WORK FROM BC TO B’C, FROM TWO TO THREE HOURS, IS HOWEVER IMPOSSIBLE WITHOUT A CONTRACTION FROM AB TO AB’, OF THE NECESSARY WORK FROM NINE TO TEN HOURS. THE SHORTENING OF THE NECESSARY WORK WOULD THUS CORRESPOND TO THE PROLONGATION OF SURPLUS LABOUR, OR PART OF THE TIME THAT UNTIL NOW THE WORKER ACTUALLY CONSUMES FOR HIMSELF, WOULD BE TRANSFORMED INTO WORKING TIME FOR THE CAPITALIST. THE LIMITS OF THE DAY WOULD NOT BE CHANGED, BUT ITS DIVISION INTO NECESSARY AND OVERWORKED WORK.