a particular time. We can, even in this case, seldom determine more than what are the most usual wages. But even this can seldom be done with regard to the profits of stock. Profit is so very fluctuating that the person who carries on a particular trade cannot always tell you himself what is the average of his annual profit. It is affected not only by every variation of price in the commodities which he deals in, but by the good or bad fortune both of his rivals and of his customers, and by a thousand other accidents to which goods when carried either by sea or by land, or even when stored in a warehouse, are liable.

It varies, therefore, not only from year to year, but from day to day, and almost from hour to hour. To ascertain what is the average profit of all the different trades carried on in a great kingdom must be