THE REVERSAL OF MALTHUS 17
estimated that after the land was cleared and ready for cultiva- tion, in the early part of the present" century, it demanded the labor of at least one man to supply the wants of ten draft ani- mals. Even this estimate is open to criticism, as below rather than above the average. Accepting it as sufficiently correct, however, it makes evident what a large contingent of the labor- force now applied to the production of human food-products would have been diverted into another channel by the continu- ance of old methods.
Science and invention have greatly increased the supply of force both by the prevention of waste of perishable crops, and by the utilization of natural and artificial products in place of purely agricultural ones, since the days of Malthus. One of the best illustrations of this is the substitution of mineral for animal and vegetable oils for illuminating and lubricating purposes. Ani- mal and vegetable fats being practically excluded from these fields of utility, by the discovery of petroleum, after a time became most serious competitors in the provinces of legitimate agricultural production. "Oleomargarine" and "filled cheese " are familiar instances of this. Within a few years the city of Chicago produced more tons of "artificial" butter than any state of the Union could show of the genuine article. " Filled cheese" has destroyed the foreign market, which was formerly so good, for the American dairy product, and so reduced the price of the unadulterated article as to make its manufacture quite unprofitable.
The canning and " cold storage " of products which were until within a very recent period so perishable as to enter into the con- sumption only during brief periods of each year, and over lim- ited areas, have transformed them into considerable ingredients of the world's supply of staple necessaries. Vegetables, fruits, and fish have thus come fnto direct competition with grains and meats, thereby still farther increasing the disparity between the demand and supply of agricultural foods. In this way the unused surplus of agricultural products and their equivalents is year by year swelled, to the manifest disadvantage of the producer, and to
