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 the latter, so as to fill that also. Supposing, then, that the steam should here only be condensed, by being brought into contact with cold water, or any other convenient means, a vacuum would be produced, into which, as a vent, more steam would immediately rush from the cylinder; this steam would also be condensed; and so the process would go on, till all the steam had left the cylinder, and a perfect vacuum had been effected in that vessel, without so much as a drop of cold water having touched or entered it. The separate vessel alone, or the condenser, would be cooled by the water used to condense the steam; which, instead of being an evil, would tend to quicken and promote the condensation. Experiments fully confirmed Watt in these views; and the consequence was, not only a saving of three-fourths of the fuel formerly required to feed the engine, but a considerable increase of its power.

In overcoming this difficulty, Watt was conducted to another improvement, which effected the complete removal of what we have described as the second radical imperfection of Newcomen's engine, namely, its non-employment, for a moving power, of the expansive force of the steam. The effectual way, it occurred to him, of preventing any air from escaping into the parts of the cylinder below the piston, would be to dispense with the use of that element above the piston, and to substitute there likewise the same contrivance as below, of alternate steam and a vacuum. This was to be accomplished by merely opening communications from the upper part of the cylinder to the boiler, on the one hand, and the condenser on the other; and forming it, at the same time, into an air-tight chamber, by means of a cover, with only a hole in it to admit the rod or shank of the piston, which might, besides, without impeding its freedom of action, be padded with hemp, the more completely to exclude the air. It was so contrived, accordingly, by a proper arrangement of the cocks, and the machinery connected with them, that while there was a vacuum in one end of the cylinder, there should be an admission of steam into the other; and the steam so admitted now served, not only by its susceptibility of sudden condensation, to create the vacuum, but also, by its expansive force, to impel the piston.

These were the principal fundamental improvements in an engine, which has since been brought to such perfection of action and power, as to form one of the most triumphant eras in the history of human ingenuity. Instead of entering into all the subsequent contrivances which Watt invented, we cannot give a better idea of his splendid success, than by quoting the language of a recent writer. 'In the present state of the engine, it appears a thing almost endowed with intelligence. It regulates, with perfect accuracy and uniformity, the number of its strokes in a given time, counting or recording them, moreover, to tell how much work it has done, as a clock records the beats of its pendulum; it regulates the quantity of steam admitted to work; the briskness of the fire, the supply of water to the boiler; the supply of coals to the fire; it opens and shuts its valves with absolute precision as to time and manner; it oils its joints; it takes out any air which may accidentally enter into parts which should be vacuous; and, when anything goes wrong, which it cannot of itself rectify, it warns its attendants by ringing a bell; yet, with all these talents and qualities, and even when exerting the power of six hundred horses, it is obedient to the hand of a child; its aliment is coal, wood, charcoal, or