Aside from windmills, sails arc the chief method of using the power of the wind. In China wheelbarrows as well as ships are pro pelled in this way. Although wind-power is very cheap its use for ships has greatly declined, and the same is true of windmills. In 1800 all ocean vessels were propelled by the wind, for steamboats were still unknown. In 1870 the number of vessels of the two kinds in Great Britain was about equal. In 1914, just before the Great War, the steam tonnage of Great Britain was over twenty times as large as the sailing tonnage. In the United States the steam tonnage is now over ten times as large as the other. We have a large proportion of sailing vessels because they are adapted to coastwise trade, which our laws encourage, while for transoceanic trade, which our laws have rarely encouraged, steam vessels are almost universally employed. Even in our own country, however, the use of sailing vessels is rapidly declining.
The reason for the decline in the use of wind-power is that the wind may die down just when it is most needed, whereas gasoline and other engines have become more and more reliable. If one of the readers of this book should invent a cheap storage battery, it would enable the power of high winds to be saved for times when there is no wind. Such an invention would go far toward solving the great problem of how the world shall continue to have cheap power when such fuels as coal and petroleum are exhausted or have risen to exorbitant prices.
(4) Water Power.—This subject is considered in Chapter VI, on "Inland Waters," and should be reviewed at this point.
(5) Wood as a Source of Power.—The sources of power thus far considered fall into two great types, (a) the power derived from living beings, including both animals and man, and (b) that derived from the movement of air and water. We must now consider a third type, (c), the power obtained by burning fuel. Fuel may be burned slowly as in a fire or explosively as in a gasoline engine. The three chief forms of fuel are wood, coal, and petroleum. Let us see what special geographical conditions cause one to be used rather than the others.
Although wood was originally of great importance as a source of power, its use for that purpose has reached a low ebb in more advanced regions.
In such regions transportation systems and farmers almost never use wood for power, and factories use it only for special reasons. Furniture factories have such a reason because they can use their own sawdust, shavings, and chips.
Again at the Swedish iron works at Dannemora iron ore is smelted with wood in the form of charcoal. This is partly because the surrounding forests furnish a vast supply of wood, but chiefly because certain of the finest grades of tool steel can be made only with char coal.
In backward regions which comprise more than half the earth's habitable surface, wood is still the chief source of power. This is the case chiefly in heavily forested regions, or else in backward countries where the difficulties of transportation make coal unduly expensive.
In the vast forested plains of northern Russia and Siberia, for example the great piles of cordwood that one sees stacked up beside the rail ways are fed into the locomotives and produce a shower of sparks equal to a Fourth of July celebration. In tropical regions, too, the river steamers often stop for hours on the edge of the forest to let a crowd of half-naked black men throw sticks of firewood upon the deck.
In such backward regions the factories as well as the transporta tion systems commonly use wood for fuel. Beth in number and size, however, the factories that use wood are insignificant. For instance, in tropical countries the scattered little sugar mills; hemp factories, canning factories and rubber-smoking plants, are some of the kinds that depend upon wood or other vegetable fibers for fuel.
(6) Coal as a Source of Power.—If there were no coal, manufac turing could be carried on by means of wood and waterpower, but its development on a large scale would be impossible. Factories require so much fuel that on the present scale they would soon exhaust the world's wood supply. The United States mines about 600,000,000 tons of coal each year. To get an equal supply of power from wood would require one and a half billion tons of cordwood which would be three or four times as much as all the wood used each year in the United States for both fuel and lumber.
How the Use of Coal Varies.—(1) Progressive Countries with Much Coal.—The distribution of coal is highly favorable. Large supplies happen to be located in places where the people are physically active and have alert, inventim minds. The countries of the world may be divided into four groups according to the activity of the people and the abundance of coal. The first group consists of progressive countries with much coal. It includes Europe from Poland, Czecho slovakia, and Austria westward, and the northeastern quarter of the United States east of the Mississippi. Not every part of these regions has coal at its very doors, but all can bring it without difficulty and therefore share in its benefits. In England, more than elsewhere great supplies of coal, as well as iron, in the midst of a large popula, tion gave the steam engine full opportunity to develop. In pro portion to its size Great Britain has much the deposits of coal in The United States, to be sure, has much _ more coal than Great Britain, and for household use Pennsylvania anthracite is better than even the finest Welsh coal, but this country is thirty-four times as large as Great Britain. The extent to which coal is mined in various countries may be judged from the fact that Britain produces over 6 tons for each inhabitant, the United States 6, Germany 4, and Belgium 3. In proportion to their population these four countries are the greatest producers of coal. They are also the leading manufacturing countries.