It is a practical fact that chickens are hatched by the thousand by the electrical current, and that men have discovered more than nature knew about the period of incubation, and have reduced it by electricity from twenty-one to nineteen days. The proverb about the value of the time of the incubating hen has passed into antiquity with all things else in the presence of electrical science. Whenever an American mechanician, a manufacturer or an inventor, is confronted by a difficulty otherwise insolvable he turns to electricity. Its laws and qualities are few. They seem now to be nearly all known, but the great curiosity of modern times is the almost infinite number of applications which these laws and qualities may be made to serve. One may turn at a single glance from the loading and firing of naval guns to the hatching of chickens and the cooking of chocolate by precisely the same means, silently used in the same way. Most of these applications, and all the most extraordinary ones, are of American origin. Their inventors are largely unknown. There is no attempt made here to more than suggest the possibilities of the near future by a glimpse of the present. The generation that is rising, the boy who is ten years old, should easily know more of electrical science than Franklin did. There are certain primal laws by which all explanations of all that now is, and most probably of almost all that is to come so far as principles go, may be readily understood, and these I have endeavored, in this and preceding chapters, to explain. There are in the United States new applications of electricity literally every day. Before the written page is printed some startling application is likely to be made that gives to that page at once an incompleteness it is impossible to guard against or avoid. There is a strong inclination to prophesy; to tell of that which is to come; to picture the warmed and illuminated future, smokeless and odorless, and the homes in which the children of the near future shall be reared. Some of those few apprehended things, suggested as being possible or desirable in these chapters, have been since done and the author has seen them. This American facility of electrical invention has one great cause, one specific reason for its fruitfulness. It is because so many acute minds have mastered the simple laws of electrical action. This knowledge not only fosters intelligent and fruitful experiment but it prevents the doing of foolish things. No man who has acquired a knowledge of mechanical forces, who understands at least that great law that for all force exerted there is exacted an equivalent, ever dreams upon the folly of the perpetual motion. In like manner does a knowledge, purely theoretical, of the laws of electricity prevent that waste of time in gropings and dreams of which the story of science and the long human struggle in all ages and in all departments is full.