Note 1 — Chapter VII · THE MARCH OF SCIENCE

If we need any motive power other than electricity, or if we need motive power of some other kind to produce electricity, no doubt the explosive recombination of oxygen and hydrogen, controlled by devices developed from existing gas-engines and petrol-engines, will be a starting-point: because coal will, probably before the complete exhaustion of the supply of it, have been found altogether too dirty and unhealthy a thing to use, at all events by way of combustion, though rumours are heard from time to time of new methods by which the stored energy of coal may be utilised directly, to the great economy of the material.1 In all sorts of ways the early years of the century will be employing themselves in seeking out new sources of man’s chief necessity—power: and a hundred years hence we shall have entered upon the full inheritance of them.