Broadly speaking, the market movements of all negotiable securities are controlled by two influences, sometimes acting in opposition to each other and sometimes in concert. One of these influences is the loaning rate of free capital; the other is the general condition of business. A low rate of interest or the likelihood of low rates has the effect of stimulating security prices, because banks and other money-lending institutions are forced into the investment market when they can not loan money to advantage. Conversely, a high rate of interest or the prospect of high rates has the effect of depressing prices, because banking institutions sell their securities in order to lend the money so released. The automatic working of this process tends to produce a constant adjustment between the yields upon free and invested capital. When money rates are low, securities tend to advance to the point where the return upon them is no greater than that derived from the loaning of free capital. When rates are high, securities tend to decline to a point where the return is as great. This explains the influence of the first factor. The other factor is the general condition of business. Good business conditions, or the promise of good conditions, tend to advance security prices, because they indicate larger earnings and a stronger financial condition. Poor business conditions, or an unpromising outlook, have the reverse effect. The larger movements of security prices are always the resultant of the interaction of these two forces. When they work together the effect is irresistible, as when low interest rates and the prospect of good business conditions occur together, or when high money rates occur in the face of an indicated falling off in business activity. At such times all classes of securities swing together. For the most part, however, money rates and business conditions are opposed in their influence, rates being low when business is bad and high when business is good. Usually the worse business conditions become, the easier money grows; while the more active business becomes, the higher money rates rise. The effect of this antagonism between the controlling causes is to produce movements of different proportions and sometimes in different directions in different classes of securities. High-grade bonds may be declining, middle-grade bonds remaining stationary, and poor bonds advancing, all at the same time. This serves to give a very irregular appearance to the security markets, and appears to justify the widely held opinion that security prices are a pure matter of guesswork, and that they are controlled only by manipulation and special influences. A clear conception of the nature of the influences which are always silently at work reconciles these apparent inconsistencies and makes it plain that general price movements are determined by laws as certain in their operation as the laws of nature.