The fluctuations of supply and prices for series of years are exhibited in the Charts 4, 5, 6, 8, 9 and 12, and these are explained in detail at the close of the chapter.
_Fluctuations with season._--Every product of the farm is known to have conditions favorable or unfavorable from the mere changes of season affecting the prospective supply. Conditions equally dependent upon the seasons have something to do with demand. The result of both combined is worthy of study by farmers and dealers in farm produce, that all may get the full benefit of such knowledge as the study affords. For this purpose, charts showing the annual fluctuations of staple products in the leading markets have been carefully prepared. These may have a greater usefulness than simply to illustrate the law of supply and demand, since it is within the possibility of actual practice to in some degree modify by provident foresight the extremes of fluctuation. It is hoped that the suggestiveness of these charts may help the most enterprising farmers to adjust their practice to conditions of market.
Charts Nos. 7, 10, 11 and 13 illustrate the fluctuations as related to seasons.
_Law of diminishing returns._--In considering the value of farm products, it is necessary to notice a natural tendency in all products of the earth toward greater cost of effort in production. This is called the law of diminishing returns, and is illustrated in every industry where the accumulations of nature are depended upon for making labor effective. Hunting, fishing and mining afford familiar illustrations of more work of the same kind for equal product.
Agriculture, however, gives the most extensive available illustration of the facts grouped under this law. In the first place, the farmer is subject to it by mere location. The product of a field near his house and barn costs less exertion than the product of a more distant field. In the second place, he is likely to have chosen for his first efforts in crop raising the land most readily yielding its fertility in crops. If he extends his operations to less productive soil, he must work more for the same product. In the third place, if a certain amount of work upon a certain field will give him twenty bushels of wheat, he must give a good deal more than twice as much work in the way of tillage and manufactured fertilizer to make a crop of forty bushels. The proof of this is clear in the disposition of farmers to buy more land instead of to increase labor upon a limited space possessed.