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 trouble to follow the table of figures and notice the fluctuations from year to year. 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. Advertising 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 limited 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.

From Data, Chicago

Fig. 74. Prices of Cement, per Barrel, in Bulk, at the Mill, from 1880 to 1910

Columns of printed figures or a series of vertical bars could not portray this information as vividly as it is brought out by the curve shown above

It would be almost impossible to give a clear idea of the flood indicated in Fig. 76 if only columns of figures were used. With the curve it can be seen clearly that the stream rose very rapidly and subsided rapidly, so that the stream was down almost to normal level within forty-eight hours after the beginning of the flood. This curve was probably plotted from flood-gauge readings taken once an