as further the mass of surplus-value which a single labourer produces, the value of labour-power being given, is determined by the rate of the surplus-value, this law follows: the mass of the surplus-value produced is equal to the amount of the variable capital advanced, multiplied by the rate of surplus-value; in other words: it is determined by the compound ratio between the number of labour-powers exploited simultaneously by the same capitalist and the degree of exploitation of each individual labour-power.
Let the mass of the surplus-value be S, the surplus-value supplied by the individual labourer in the average day s, the variable capital daily advanced in the purchase of one individual labour-power v, the sum total of the variable capital V, the value of an average labour-power P, its degree of exploitation a′ (surplus-labor)a (necessary-labor) and the number of labourers employed n; we have:
| S = | sv×V |
| P×a′a×n |
It is always supposed, not only that the value of an average labour-power is constant, but that the labourers employed by a capitalist are reduced to average labourers. There are exceptional cases in which the surplus-value produced does not increase in proportion to the number of labourers exploited, but then the value of the labour-power does not remain constant.
In the production of a definite mass of surplus-value, therefore, the decrease of one factor may be compensated by the increase of the other. If the variable capital diminishes, and at the same time the rate of surplus-value increases in the same ratio, the mass of surplus-value produced remains unaltered. If on our earlier assumption the capitalist must advance 300s., in order to exploit 100 labourers a day, and if the rate of surplus-value amounts to 50%, this variable capital of 300s. yields a surplus-value of 150s. or of 100×3 working hours. If the rate of surplus-value doubles, or the working day, in-
