On the same principle, if for the production of an English commodity, 300 days labour were advanced in fixed capital for a year, and 1500 days labour were consumed on the commodity in the same time, while profits were 10 per cent., the natural value of such commodity, or the conditions of its supply, would be 1500 days labour, with a profit of 10 per cent. upon 1800, which together would equal 1680: and if labour were two shillings a day, the natural price at which the commodity would circulate, and according to which it would exchange with any foreign commodity brought to England, would be £168. This prodigious difference in the natural prices of two commodities in England and India, the natural values of which in each country were nearly the same, could only arise from a difference in the value of money occasioned by the very superior efficiency of English labour in the purchase of the precious metals, owing to the energy, skill, and situation of English labourers and capitalists, compared with those of India. But in estimating this difference in the value of money in England and India, it is quite obvious, that if, after ascertaining the natural conditions of the supply of a commodity in each country, we were to estimate the value of money either by its general power of purchasing, by a mean between corn and labour,[F] or by the quantity of labour alone which had been actually employed in bringing the money from the mine to the market, or by any other measure whatever, except the labour which it would command, we should not account for the natural prices which are found actually to prevail in the two countries, and according to which Indian and English commodities are found to exchange with each other by experience. Consequently, as no other supposition will suit the actual phenomena, and as it has already appeared that the value of commodities in the same country is determined by the quantity of labour which they will command, we may safely conclude that the value of the precious metals in different countries is determined by the same measure, or by the different quantities of common agricultural labour, taking the average of summer and winter wages, which a given portion of them will command. * * * * * When we come to consider the varying value of commodities at distant periods in the same country, or the rise or fall of produce in the progress of cultivation and improvement, we are necessarily deprived of the test of an actual exchange. We know, however, that at different periods in the same country both the value of the precious metals, and the rate of profits and corn wages, may alter most essentially.