preferability of treasure to other forms of wealth, on the balance of trade, and on the policy of restriction generally are contradictory, not to say vacillating. On almost all questions of public revenue and public expenditure, on the contrary, his opinions are well developed, clear and consistent. The great changes in the fiscal system which were made by the Convention Parliament gave rise to no other discussion at all comparable with his "Treatise of Taxes and Contributions[1];" and it is scarcely too much to say that English economic literature before Hume can show no tract of such range and force, characterized by such wealth of suggestion and such power of analysis, as is Petty's masterpiece. It contains the germ of nearly every theory which he afterwards elaborated. Even his method of political arithmetic is exemplified in the calculations of its second chapter[2]. The calculations are, to be sure, both slight and unsatisfactory; but rather from lack of trustworthy data than from any failure on Petty's part to appreciate the importance of such devices. On the contrary he demands for economic purposes a thorough survey of lands and their produce [3], and of money, wages and population, for "until this be done trade will be too conjectural a work for any man to employ his thoughts about[4]." Before the publication of the "Treatise" he was indeed acquainted with Graunt's "Observations[5]," but the suggestions of that book had not had as yet sufficient time to exert their full influence upon him. Consequently the number of the people, which becomes in the "Verbum Sapienti" (1664) a key to the national wealth, and thus affords a basis for the distribution of taxation much more satisfactory than expenditure[6], is used in the "Treatise" but incidentally to a minor question of retrenchment[7].
To the problem of national wealth Petty never tires of applying the methods of his political arithmetic. The "Verbum Sapienti" shows both the reason that led him to attack the problem and the method which he employed for its solution. The introduction explains that taxation is unequal, "which disproportion is the true and proper grievance of taxes[8]." To the end that the public charge be laid proportionally it is necessary that the total effects of the
