Continuing, Mill says: “The operations of speculative dealers are useful to the public whenever profitable to themselves. The interest of the speculators as a body coincide with the interests of the public; and as they can only fail to serve the public interest in proportion as they miss their own, _the best way to promote the one is to leave them to pursue the other in perfect freedom. Neither law nor opinion should prevent an operation, beneficial to the public, from being attended with as much private advantage as is compatible with full and free competition_.” Mill makes no distinction here between investors and speculators; they are one and the same. In any case it is conceded that speculation is what makes the markets to-day, since 90 per cent. of the transactions that take place daily on the world’s Stock Exchanges are speculations pure and simple. And this is a good thing. Before we go on with our subject, let Professor Emery explain why, and bring the teachings of McCulloch and Mill down to our own day: “Speculation has become an increasingly important factor in the economic world without receiving a corresponding place in economic science. In the field in which it acts, in the trade in grain and cotton and securities and the like, speculation is the predominant influence in determining price, and, as such, is one of the chief directive forces in trade and industry. But treatises in the English language on general economic theory and conditions have given very little space to this influence, which is fundamental in the world of economic fact.... “It is true that forty years ago speculation was far less important than it is now, and there was, therefore, more justification for disregarding it. Professor Hadley has given due consideration to the new conditions which prevail in modern business. At the same time it should be remembered that McCulloch, already in his day, had grasped the true idea of the function of speculation, a fact shown by the incorporation of his treatment of the subject into his chapters on Value. Wide as is the influence of speculation, its force is felt primarily in the field of prices. By making prices it directs industry and trade, for men produce and exchange according to comparative prices. Speculation then is vitally connected with the theory of value.