methods of statistical study were little appreciated, and few of these writers seem to have made serious efforts to check the accuracy of the figures on which they relied. Petty, of course, stands by himself as a pioneer; his work was of unexampled excellence, but those who imitated his studies were very far from following his example. In some cases those who did not attempt to compute the changes in England as a whole were satisfied to take one branch of trade as exemplifying all the rest.[1] There was still one department of economic life which had a peculiar interest for Englishmen, and which was treated as of special importance—this was the maintenance of shipping as the means of offence and defence; but this was regarded as an object of policy towards which the Government were bound to direct the three factors which increased wealth. It was a matter of public importance; and the art of government, as it was conceived in the eighteenth century, consisted in so guiding the private interest of individuals that they might work for the public good. In the sixteenth century moralists had written of private interest as if it were invariably hostile to public advantage. Men were expected to carry on their trade in a public-spirited fashion and not to regard their private lucre; but in the eighteenth century the force of self-interest was recognized as a power that was rather indifferent than hostile to the public good, so that it seemed as if a very moderate amount of direction might be brought to bear, and thus induce men who were guided by self-interest alone to carry on their business in a manner that accorded with public prosperity.[2]
Although it was particularly important to measure the improvement or decay of any of the factors which made for the production of wealth, it was by no means easy to do so. Political arithmeticians could, however. note symptoms which were specially striking; and they could look either at the results of our industry (agricultural and manufacturing) or at the conditions under which it was carried on,—these conditions having reference both to the facilities for procuring capital and to the effectiveness of Labour. These three points were most easily examined by considering three criteria, first the Balance of Trade, as showing the profitableness of our commercial intercourse with various countries; second, the rate of interest as showing the facility with which capital might
