All About Engines

Fuel and Its Problems 341 ♦ and alcohol can, as we have seen, be used as a fuel for internal combustion engines. Probably the most suitable substance to grow for this purpose would be beet, because the plant itself in the course of its giowth produces a large quantity of sugar and shortens the process which would be necessary if cellulose were the starting point. But it is very doubtful whether the demand for power could be wholly met in this way, though it is a striking fact that before the war the beer and wine produced annually in the world contained about 5 million tons of alcohol. It would be curious in- deed if what a man takes to warm his interior should prove to be more valuable for wanning his exterior ; and still more curious if the motor cyclist of the future should stop a,t a wayside inn to beg- a glass of water for himself and purchase a drink for his engine ! It may be, indeed, that water will ultimately turn out to be the salvation of both. Dame Nature is not so bad a mother, after all, for in many parts of the earth stæ has provided a, sourc© of power which is inexhaustible—a source which may be a little capricious and uncertain, but which, so long as the sun shines and the wind blows and the rain falls will never fo.il. F or undei the influence of th.6 sun the air takes up moisture from the great oceans, and the wind carries it towards the land. Local varia- tions of temperature arising from atmospheric cir- culation cause some of this to be thrown out as rain on land and sea alike; but the main precipitation