To this theory Cairnes objects that wages, being remuneration, can in no sense be considered as cost, and could only have come to be regarded as cost in consequence of the whole problem being treated from the point of view of the capitalist, to whom, no doubt, the wages paid represent cost. The real elements of cost of production he looks upon as labour, abstinence and risk, the second of these falling mainly, though not necessarily, upon the capitalist. In this analysis he to a considerable extent follows and improves upon Nassau William Senior, who had previously defined cost of production as the sum of the labour and abstinence necessary to production. Cairnes' exposition of the natural or social limit to free competition, and of its bearing on the theory of value: He points out that in any organised society there can hardly be the ready transference of capital from one employment to another, which is the indispensable condition of free competition; while class distinctions render it impossible for labour to transfer itself readily to new occupations. Society may thus be regarded as consisting of a series of noncompeting industrial groups, with free competition among the members of any one group or class. Now the only condition under which cost of production will regulate value is perfect competition. It follows that the normal value of commodities-the value which gives to the producers the average and usual remuneration will depend upon cost of production only when the exchange is confined to the members of one class, among whom there is free competition. In exchange between classes or non-competing industrial groups, the normal value is simply a case of international value, and depends upon reciprocal demand, that is to say, is such as will satisfy the equation of demand. This theory is a substantial contribution to economical science and throws great light upon the general problem of value. At the same time, it may be thought that Cairnes overlooked a point brought forward prominently by Senior, who also had called attention to the bearing of competition on the relation between cost of production and value. The cost to the producer fixes the limit below which the price cannot fall without the supply being affected; but it is the desire of the consumer-i.e. what he is willing to give up rather than be compelled to produce the commodity for himself that fixes the