Wages themselves again take many forms, a fact not recognizable in the ordinary economic treatises which, exclusively interested in the material side of the question, neglect every difference of form. An exposition of all these forms however, belongs to the special study of wage labour, not therefore to this work. Still the two fundamental forms must be briefly worked out here. The sale of labour-power, as will be remembered, takes place for a definite period of time. The converted form under which the daily, weekly, &c., value of labour-power presents itself, is hence that of time-wages, therefore day-wages, &c. Next it is to be noted that the laws set forth, in the 17th chapter, on the changes in the relative magnitudes of price of labour-power and surplus-value, pass by a simple transformation of form, into laws of wages. Similarly the distinction between the exchange-value of labour power, and the sum of the necessaries of life into which this value is converted, now reappears as the distinction between nominal and real wages. It would be useless to repeat here, with regard to the phenomenal form, what has been already worked out in the substantial form. We limit ourselves therefore to a few points characteristic of time-wages. The sum of money  which the labourer receives for his daily or weekly labour, forms the amount of his nominal wages, or of his wages estimated in value. But it is clear that according to the length of the working-day, that is, according to the amount of actual labour daily supplied, the same daily or weekly wage may represent very different prices of labour, i.e., very different sums of money for the same quantity of labour.  We must, therefore, in considering time-wages, again distinguish between the sum-total of the daily or weekly wages, &c., and the price of labour. How then, to find this price, i.e., the money-value of a given quantity of labour? The average price of labour is found, when the average daily value of the labour-power is divided by the average number of hours in the working-day. If, e.g., the daily value of labour-power is 3 shillings, the value of the product of 6 working-hours, and if the working-day is 12 hours, the price of 1 working hour is 3/12 shillings = 3d. The price of the working-hour thus found serves as the unit measure for the price of labour. It follows therefore that the daily and weekly wages, &c., may remain the same, although the price of labour falls constantly. If, e.g., the habitual working-day is 10 hours and the daily value of the labour-power 3s., the price of the working-hour is 3 3/5d. It falls to 3d. as soon as the working-day rises to 12 hours, to 2 2/5d as soon as it rises to 15 hours. Daily or weekly wages remain, despite all this, unchanged. On the contrary, the daily or weekly wages may rise, although the price of labour remains constant or even falls. If, e.g., the working-day is 10 hours, and the daily value of labour-power 3 shillings, the price of one working-hour is 3 3/5d. If the labourer, in consequence of increase of trade, works 12 hours, the price of labour remaining the same, his daily wage now rises to 3 shillings 7 1/5 d. without any variation in the price of labour. The same result might follow if, instead of the extensive amount of labour, its intensive amount increased.  The rise of the nominal daily or weekly wages may therefore be accompanied by a price of labour that remains stationary or falls. The same holds as to the income of the labourer s family, as soon as the quantity of labour expended by the head of the family is increased by the labour of the members of his family. There are, therefore, methods of lowering the price of labour independent of the reduction of the nominal daily or weekly wages.  As a general law it follows that, given the amount of daily or weekly labour, &c., the daily or weekly wages depend on the price of labour which itself varies either with the value of labour-power, or with the difference between its price and its value. Given, on the other hand, the price of labour, the daily or weekly wages depend on the quantity of the daily or weekly labour. The unit-measure for time-wages, the price of the working-hour, is the quotient of the value of a day s labour-power, divided by the number of hours of the average working-day. Let the latter be 12 hours, and the daily value of labour-power 3 shillings, the value of the product of 6 hours of labour. Under these circumstances the price of a working hour is 3d.; the value produced in it is 6d. If the labourer is now employed less than 12 hours (or less than 6 days in the week), e.g., only 6 or 8 hours, he receives, with this price of labour, only 2s. or 1s. 6d. a day.  As on our hypothesis he must work on the average 6 hours daily, in order to produce a day s wage corresponding merely to the value of his labour power, as according to the same hypothesis he works only half of every hour for himself, and half for the capitalist, it is clear that he cannot obtain for himself the value of the product of 6 hours if he is employed less than 12 hours. In previous chapters we saw the destructive consequences of over-work; here we find the sources of the sufferings that result to the labourer from his insufficient employment. If the hour s wage is fixed so that the capitalist does not bind himself to pay a day s or a week s wage, but only to pay wages for the hours during which he chooses to employ the labourer, he can employ him for a shorter time than that which is originally the basis of the calculation of the hour-wage, or the unit-measure of the price of labour. Since this unit is determined by the ratio daily value of labour-power working-day of a given number of hours With an increasing daily or weekly wage the price of labour may remain nominally constant, and yet may fall below its normal level. This occurs every time that, the price of labour (reckoned per working-hour) remaining constant, the working-day is prolonged beyond its customary length. If in the fraction: daily value of labour power working-day It is a fact generally known that, the longer the working-days, in any branch of industry, the lower are the wages.  A. Redgrave, factory inspector, illustrates this by a comparative review of the 20 years from 1839-1859, according to which wages rose in the factories under the 10 Hours Law, whilst they fell in the factories in which the work lasted 14 to 15 hours daily.  From the law, the price of labour being given, the daily or weekly wage depends on the quantity of labour expended, it follows, first of all, that the lower the price of labour, the greater must be the quantity of labour, or the longer must be the working-day for the labourer to secure even a miserable average wage. The lowness of the price of labour acts here as a stimulus to the extension of the labour-time.  On the other hand, the extension of the working-time produces, in its turn, a fall in the price of labour, and with this a fall in the day s or week s wages. The determination of the price of labour by: daily value of labour power working day of a given number of hours This jeremiad is also interesting because it shows how the appearance only of the relations of production mirrors itself in the brain of the capitalist. The capitalist does not know that the normal price of labour also includes a definite quantity of unpaid labour, and that this very unpaid labour is the normal source of his gain. The category of surplus labour-time does not exist at all for him, since it is included in the normal working-day, which he thinks he has paid for in the day s wages. But over-time does exist for him, the prolongation of the working-day beyond the limits corresponding with the usual price of labour. Face to face with his underselling competitor, he even insists upon extra pay for this over-time. He again does not know that this extra pay includes unpaid labour, just as well as does the price of the customary hour of labour. For example, the price of one hour of the 12 hours working-day is 3d., say the value-product of half a working-hour, whilst the price of the over-time working-hour is 4d., or the value-product of 2/3 of a working hour. In the first case the capitalist appropriates to himself one-half, in the second, one-third of the working-hour without paying for it. 
Economic Manuscripts: Capital Vol. I - Chapter Twenty