=376. Petroleum.=—Nor is the new commercial significance of mineral products confined to the metals. In the last half century the trade in mineral oil (petroleum, “kerosene”) has become a necessary part of the world’s economy. One result of the great improvements in manufactures and transportation was a demand, from all sides, for more light. Artificial illumination was needed for the full utilization of machinery and means of transportation; and to provide light for the newspaper reading, study, and recreation to which people gave themselves in increasing numbers. The first half of the century witnessed many improvements: the invention of matches, the introduction of glass lamp-chimneys, the spread of gas lighting, and the use of new oils for illumination. No previous advance, however, compares in importance with the discovery that crude petroleum could be made the source of a cheap and efficient means of illumination. The development of the petroleum trade in the space of little more than a generation is a matter of common knowledge, and is readily explained by the importance of the service which it performs. =377. The grain trade; slight development before 1800.=—Important and characteristic as the trade in mineral products has grown to be in the nineteenth century, it is still far from first place among the branches of the world’s commerce. The primacy belongs, without question, to the trade in foodstuffs, especially grain. Before the development of the modern system of transportation commerce in foodstuffs concerned itself largely with the condiments rather than the aliments, with spices and seasoning rather than the substantial food staples. Even at a freight rate of 15 cents per ton-mile (and the expense of transportation on European roads before 1800 was certainly far above that), wheat at $1.50 a bushel would be limited to a trade-radius of 330 miles; the whole value of the wheat would be consumed in transporting it that distance. Transportation by sea was, of course, much less costly, and enabled limited amounts of food to be imported under favorable conditions. Still, food has to be grown on land, and often on land distant from any means of water carriage; and the countries of Europe were forced in general to a policy of self-sufficiency, raising the requisite supplies of food at home under conditions however unfavorable. We may appreciate the short space of time separating us from this state of affairs by noting that in France, even in 1817, people were dying of famine in Lorraine, while wheat was abundant in Brittany; the carriage of provisions from one province to the other quadrupled prices. In Russia, even later (Pskov, 1845), the same conditions prevailed.