interest. And that is all there is to it. Indeed, for economic theory of this kind, that is all there is to any economic situation. The hedonistic magnitudes vary from one situation to another, but, except for variations in the arithmetical details of the hedonistic balance, all situations are, in point of economic theory, substantially alike.[8] Taking this unfaltering taxonomy on its own recognisances, let us follow the trail somewhat more into the arithmetical details, as it leads along the narrow ridge of rational calculation, above the tree-tops, on the levels of clear sunlight and moonshine. For the purpose in hand--to bring out the character of this current economic science as a working theory of current facts, and more particularly "as applied to modern problems of industry and public policy" (title-page)--the sequence to be observed in questioning the several sections into which the theoretical structure falls is not essential. The structure of classical theory is familiar to all students, and Mr. Clark's redaction offers no serious departure from the conventional lines. Such divergence from conventional lines as may occur is a matter of details, commonly of improvements in detail; and the revisions of detail do not stand in such an organic relation to one another, nor do they support and strengthen one another in such a manner, as to suggest anything like a revolutionary trend or a breaking away from the conventional lines. So as regards Mr. Clark's doctrine of Capital. It does not differ substantially from the doctrines which are gaining currency at the hands of such writers as Mr. Fisher or Mr. Fetter; although there are certain formal distinctions peculiar to Mr. Clark's exposition of the "Capital Concept." But these peculiarities are peculiarities of the method of arriving at the concept rather than peculiarities substantial to the concept itself. The main discussion of the nature of capital is contained in chapter ii. (Varieties of Economic Goods). The conception of capital here set forth is of fundamental consequence to the system, partly because of the important place assigned capital in this system of theory, partly because of the importance which the conception of capital must have in any theory that is to deal with problems of the current (capitalistic) situation. Several classes of capital-goods are enumerated, but it appears that in Mr. Clark's apprehension--at variance with Mr. Fisher's view--persons are not to be included among the items of capital. It is also clear from the run of the argument, though not explicitly stated, that only material, tangible, mechanically definable articles of wealth go to make up capital. In current usage, in the business community, "capital" is a pecuniary concept, of course, and is not definable in mechanical terms; but Mr. Clark, true to the hedonistic taxonomy, sticks by the test of mechanical demarcation and draws the