Since the division of the day's work into necessary and surplus labour differs in different countries, and even in the same country at different periods, or in different branches of industry; and further, since the actual wage of the labourer at one time sinks below the value of his labour power, at another rises above it, it is possible for the difference between the price of the machinery and the price of the labour power replaced by that machinery to vary very much, although the difference between the quantity of labour requisite to produce the machine and the total quantity replaced by it, remain constant.