Rubber and cotton illustrate the dominance of the cyclonic regions quite as forcibly as do any other products. Rubber does this in the same way as tin, for although it is a purely tropical product, it is practically all exported to a few cyclonic countries and there man ufactured. The United States consumes over half the world's rubber. Cotton iP.ustrates the matter in much the same way. Fig. 98 shows where the world's cotton crop is grown. It is clearly limited to fairly warm regions. But compare this with Fig. 44 which shows where the cotton is woven into cloth. Evidently the greater part of the cotton crop is carried to cyclonic regions and there manu factured.
Why Crops Improve as They are Moved toward Cyclonic Regions. —Cotton shows the effect of the energy of the people of cyclonic regions in still another way. The average yield of the crop per acre in the United States displays a general tendency to increase toward the north. Near the northern limit in southern Missouri and Vir ginia the yield per acre is about twice as great as in Florida and Louisiana. Like many other crops, cotton naturally grows best in about the middle of its geographical range. We see this in all wild plants. The best pine trees, for example, grow neither in the far north nor the far south; the holly is a little bush in New England, it becomes a great tree in the Southern States, where it thrives best; while still farther south it again diminishes in vigor. So, too, with thousands of other wild plants, both great and small. Yet among cultivated plants derived originally from warmer climes, not only cotton, but corn, wheat, potatoes, oranges, grape fruit, and others grow best at their northern limit. In other words, when these crops are gradually moved toward the regions where man is most com petent their productivity and quality improve because of the care given them, although naturally they would not thrive in their new homes.
The Supremacy of the Cyclonic Regions in Transportation.— Figs. 109 and 33 illustrate the concentration of horses and of railways in the cyclonic regions. How far is this due to other factors than climate? Plains, especially grasslands, certainly have an effect on the distribution of horses, for there are more horses in the grassy plains of the central United States, eastern Argentine, and southwestern Russia than in the neighboring regions. But in the grassy plains of the
non-cyclonic regions of the Orinoco, and the Sudan, there are prac tically none. So, too, railroads are numerous throughout the plains of cyclonic regions, but are absent in the still greater plains of the Amazon Basin, northern Canada, northern Siberia, and Arabia.
The density of the population also has an effect on the distribution of both horses and railways, but how important is this? Compare Figs. 109 and 33 with Fig. 37, showing the distribution of popula tion. China, Java, and India are among the blackest areas on the population map, yet there is only one mile of railway for every 30 square miles of territory in Java, 50 in India, and 220 in China, while there is a mile of railway for every 11 square miles in the United States, 8 in France, 6 in Holland, and 5 in Great Britain. Moreover, both Java and India would have a railway net even less dense than that of China if they had not received railway systems from their Dutch and English rulers. Thus it appears that while relief, vegeta tion, and density of population all have some effect on the develop ment of means of transportation, the main effect is due to the cy clonic climate. In cyclonic regions the people have plenty of work for horses and plenty of freight for railways, and they also have the ability and energy to improve the breeds of horses and to invent and build railways.
If we had maps showing the world distribution of good roads, automobiles, trolley lines. or airplanes, they would all show the same pre-eminence of the cyclonic regions.
Where the World's Manufacturing is Done.—If a country. is to be prominent in manufacturing, there must be (1) coal for power,' (2) iron for machinery, but much the most important requisite is' (3) inventive energetic people to manage the factories and run the machinery. We have already seen that though iron ore is found in practically all parts of the world, it is extensively mined and smelted only in cyclonic regions. Coal follows the same rule. Although coal is less abundant in tropical countries than elsewhere, it is found in all the climatic zones, as appears in Fig. 60. Some of the finest of all deposits are in China and Indo-China. Yet almost all the mining is done in the cyclonic regions, as is clearly evident from Fig. 61.