In no way will the acceleration of the speed of progress be more apparent than in the thoughts and emotions of men. But to say this is not to belittle the progress which science and invention have in store for the new age. In applying a sort of imaginative telescope to the mental eye it will be necessary to keep constantly in view the utter inconceivableness of modern achievement by the civilised world of the past. When electricity was no more than a sort of scientific plaything--when notions of its possible uses were (as in Davy's time) far less substantially imagined than, for instance, the possible uses of radium are to-day, even scientific thinkers, endowed with what Huxley so luminously applauded as scientific imagination, had no rudiment of the materials for conceiving such inventions as the electric telegraph--far less the possibilities of transmitted and picked-up wave energy. And here, at the beginning of wireless telegraphy, we are no less in the dark as to what will develop from it and what will supersede it. The nineteenth century progressed, almost from first to last, on the strength of the discovery of how to utilise the stored energy of coal, whether directly in the steam engine or indirectly in the dynamo-electric machine and the electric motor. With the end of the coal age already well in view, we can only conjecture what the sources of mechanical power will be a hundred years hence. Before we have quite exhausted our coal measures and begun to draw more liberally on our stores of petroleum, we shall no doubt have abandoned altogether so wasteful a contrivance as the steam engine. There is a clumsiness almost barbarous in the roundabout employment of coal to produce heat, the steam engine to utilise only a miserable fraction of the potential energy even of the part of the coal which we do not fatuously allow to escape as smoke; of the dynamo to use up a part of the motion yielded by the steam engine in producing electricity (while a small but recognisable portion of that motion is converted wastefully back again into heat), and of the electro-motor to re-convert the electricity into motion, heat, light and chemical energy, according to our requirements. It cannot be many years before we learn to use coal far more economically than we do nowadays, abolishing the furnace and the steam engine, and obtaining electricity directly from coal itself by some sort of electro-chemical decomposition. But even so, our coal will not last much longer. The speed of our progress will exhaust it much sooner than most people imagine, and probably in another twenty-five years the end of our petroleum will also begin to be looked forward to with apprehension.