In 1840 Britain had only 620,000 horse-power nominal; the United States 760,000; the whole world had only 1,650,000 horse-power. To-day it has 75,000,000 nominal. So rapidly has steam extended its sway over most of the earth in less than the span of a man's life. There has never been any development in the world's history comparable to this, nor can we imagine that such a rapid transformation can ever come in the future. What the future is finally to bring forth even imagination is unable to conceive. No bounds can be set to its forthcoming possible, even probable, wonders, but as such a revolution as steam has brought must come from a superior force capable of displacing steam, this would necessarily be a much longer task than steam had in occupying an entirely new field without a rival. The contrast between Newcomen and Watt is interesting. The Newcomen engine consumed twenty-eight pounds of coal per horse-power and made not exceeding three to four strokes per minute, the piston moving about fifty feet per minute. To-day, steam marine engines on one and one-third pounds of coal per horse-power--the monster ships using less--make from seventy to ninety revolutions per minute. "Destroyers" reach 400 per minute. Small steam engines, it is stated, have attained 600 revolutions per minute. The piston to-day is supposed to travel moderately when at 1,000 feet per minute, in a cylinder three feet long. This gives 166 revolutions per minute. With coal under the boilers costing one dollar per net ton, from say five pounds of coal for one cent there is one horse-power for three hours, or a day and a night of continuous running for eight cents. Countless millions of men and of horses would be useless for the work of the steam-engine, for the seemingly miraculous quality steam possesses, that permits concentration, is as requisite as its expansive powers. One hundred thousand horse-power, or several hundred thousand horse-power, is placed under one roof and directed to the task required. Sixty-four thousand horse-power is concentrated in the hold of the great steamships now building. All this stupendous force is evolved, concentrated and regulated by science from the most unpromising of substances, cold water. Nothing man has discovered or imagined is to be named with the steam engine. It has no fellow. Franklin capturing the lightning, Morse annihilating space with the telegraph, Bell transmitting speech through the air by the telephone, are not less mysterious--being more ethereal, perhaps in one sense they are even more so--still, the labor of the world performed by heating cold water places Watt and his steam engine in a class apart by itself. Many are the inventions for applying power; his creates the power it applies.