Security operations involving a demand for foreign exchange are, however, by no means confined to American participation in foreign bond issues. Accumulated during the course of the past half century, there is a perfectly immense amount of American securities held all over Europe. The greater part of this investment is in bonds and remains untouched for years at a stretch. But then there come times when, for one reason or another, waves of selling pass over the European holdings of "Americans," and we are required to take back millions of dollars' worth of our stocks and bonds. Such selling movements do not really get very far below the surface--they do not, for instance, disturb the great blocks of American bonds in which so large a proportion of many of the big foreign fortunes are invested, but they are apt to be, nevertheless, on a scale which requires large amounts of exchange to pay for what we have had to buy back. The same thing is true with stocks, though in that case the selling movements are more frequent and less important. Europe is always interested heavily in American stocks, there being, as in the case of bonds, a big fixed investment of capital, beside a continually fluctuating "floating-investment." In other words, aside from their fixed investments in our stocks, the foreigners are continually speculating in them and continually changing their position as buyers and sellers. Selling movements such as these do not materially affect Europe's set position on our stocks, but they do result at times in very large amounts of our stocks being dumped back upon us--sometimes when we are ready for them, sometimes when the operation is decidedly painful, as in the Fall of 1907. In any case, when Europe sells, we buy. And when we buy, and at the rate of millions of dollars' worth a day, there is a big demand for exchange with which to pay for what we have bought.