the accepted truths of this Science, like those of the other developed sciences, should be practically and steadily applied to the betterment of mankind. Under these broadening and inspiriting and uplifting conditions Political Economy, as never before, thanked God and took courage. 3. Having now a satisfactory definition of Value, and knowing accordingly just what Valuables are in clear distinction from all other things in the world, we must examine with some care two or three of the most general facts and laws and limits of Value, before we pass in the next following chapters to study in detail each of the three kinds of Valuables, namely, material Commodities, personal Services, commercial Credits. (a) Since Value in general is the relation of mutual purchase between two Services, and consequently the specific value of either can only be expressed by the other,--one Valuable being always measured by the Valuable exchanged against it,--it follows as a matter of course that such a thing as a general Rise or Fall of Valuables is an impossibility. The rise of one valuable involves of necessity a fall in the other, as the fall of one implies the rise of the other. If the articles exchanged be bushels of wheat and dollars of silver, and if a bushel buys a dollar to-day, then wheat is worth a dollar a bushel; but if wheat rises next week, so that a dollar will not buy a full bushel, that is precisely the same thing as saying, that the dollar has fallen in its purchasing-power as compared with the wheat. Such specific changes in the purchasing-power of one Valuable over another are incessant throughout the commercial world, and a merchant's sagacity consists in anticipating these so far as possible and in availing himself of them alertly and prudently; but each one of us must needs see clearly and hold firmly in mind, that each fall in the purchasing-power of a Valuable means a corresponding rise of power in the other Valuable,--if the first buys more of the second than before, then the second must buy less than before of the first; and, consequently, a general rise of Valuables is a contradiction in terms, and so of course is a general fall of Valuables.