The curve, however, gives all the variations in price at a glance and shows in most striking manner the great reduction which occurred in the price of cement as manufacturing facilities improved and increased. A curve of this kind greatly stimulates thought, for one immediately wishes to know the cause of each of the peaks and of each of the valleys in the curve. One gets a vista of recurring periods of financial boom and of financial depression, and a glimpse of such factors as new developments in methods of manufacturing cement and the constantly increasing demand for the product.

If the reading of curves were understood by the average educated person, it would be possible to use, in almost any kind of magazine, advertising illustrations on the order of that shown in Fig. 75. Since, however, curves are not widely understood at present, this type of advertising must now be limited chiefly to the technical journals read by engineers and others who understand curve interpretation. It is really a calamity that curves are not more widely understood. Ad vertising men are now frequently unable to convince people of their argument simply because they have no language by means of which figures can be made interesting or even intelligible when expressed in an advertisement of hmited size. The author ventures to predict that it will be only a very few years until curves are so widely understood and used that they may be presented advantageously in any high-grade advertising pages.