Page:Popular Science Monthly Volume 76.djvu/113

Rh seemed menaced, and other natural resources had to be developed, and more efficient methods of application found. Thus in our day the development of the internal combustion or gas engine, which threatens to crowd the steam engine to the wall, has finally permitted the application of petroleum, which by the aid of chemistry has furnished not only great stores of energy, but numerous useful products. Not the least important aspect of the power development is that part which is applied to transportation. The covering of the whole known world with lines of railway has made possible and easy movements from place to place not only of peoples, but of products, so that while a few centuries ago a large proportion of the population never moved more than a few miles from their birthplaces, being as good as fettered to the soil, now even the poorest may be easily displaced from country to country, the seas being no more of a barrier than the land. The increase of education by travel, and the tendency toward peace produced by the increased acquaintance of nations with each other, is not to be overestimated. Perhaps no more impressive example of man's power over nature is to be found than the sight of a great ocean steamship, lying at her dock and towering over the surrounding buildings, or ploughing her way at express speed over the stormy waves, whose power she hardly seems to feel. A notion of the huge demands made by ocean transportation on our resources of energy is obtained when we think that one of these marine monsters is using sixty or eighty thousand horsepower, while an express train uses from a thousand to fifteen hundred only. In view of this depletion of our coal supplies the question of water power has become urgent, »and science has succeeded in bridling our rivers and waterfalls for further supplies, while the transmission of this power by electricity has made manufacturing possible where it was not before, and is now being applied to transportation on a large scale. Not to be neglected in connection with the application of power is the question of illumination. When we think of the dark and dismal nights in the cities, not only of antiquity, but even of two centuries ago, making it impossible to go out in safety at night, and encouraging all sorts of crimes of violence, we must consider the successive application of gas, oil and electricity to have had no mean influence on the habits of mankind. The use of modern illuminants, especially electrical, has made possible the performance of more work, under more healthful conditions, and has completely changed the habits of man as regards the hours of darkness. Whether this has been entirely for his advantage we may leave until later.

Almost equally important with transportation is communication, which has in like manner changed the possibilities and habits of mankind. At the time of our revolution it took weeks to get any news to