This may be illustrated by a single example. Let us assume that interest rates are low and business conditions bad with prospect of still lower interest rates and still more unpromising business conditions. What will be the effect upon different classes of securities? High-grade bonds, such as choice municipals, whose safety can not be impaired by any extent of depression in business, will advance because their market price is influenced almost wholly by money rates. If their interest is certain to be paid, no matter what business conditions may become, they can not be greatly affected by a reduction of earnings, and consequently the influence of low money rates is left to act practically alone. Middle-grade bonds, such as second-class railroad issues, will remain almost stationary, low money rates tending to advance their price and the fear of decreased earnings tending to depress them. The lowest grade of bonds and stocks, whose margin of security even in good times is not very great, will probably suffer in price because the fear of default in interest and of reduction in dividends will operate much more strongly than the mere stimulus of low interest rates. Of course, securities can not be clearly separated into these three classes, but shade imperceptibly into one another. The classification is adopted only for purposes of illustration. Up to this point we have been concerned merely in showing that the market movements of negotiable securities are controlled by the influence of certain factors. A more important question now remains to be considered, viz.: whether the effect of these two influences is to produce general swings in prices which may be depended upon with comparative certainty, and, if so, what indications are afforded to the investor of the commencement or culmination of such a movement. The answer must be that the combined effect of the two influences described is to produce definite and regular swings in prices, and that the indications which define the movements are not difficult to follow.