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EARLY APPLICATIONS OF STEAM POWER. 19

CHAPTER II.

EARLY APPLICATIONS OF STEAM POWER.

13. General Remarks.-In the preceding chapter have been explained the natural phenomena on which the sources of steam power depend. But these forces cannot be made immediately applicable to the purposes of locomotion: an upward force may be required, but water falls downward; a circular motion may be wanted, but the impelling power of wind is rectilinear; a particular direction may be necessary in which the pressure of steam is to be exerted, but steam presses with equal force in every direction; in a word, the motion of the impelling power may be of one kind, and that required at the working point, of another and very different kind. The forces, therefore, which actually exist in nature, or are called into existence by art, must be determined to the purposes required, by means of machinery, the great object of which is change, or modification, of motion. A vertical motion, for instance, being produced by the fall of a stream of water, a circular motion is readily procured by the introduction of a wheel furnished with cavities around its circumference; the paddle-wheel of a steam-boat furnishes an example of a continued rectilinear, produced by a continued circular, motion; an undershot water-wheel affords a continued circular, produced by a continued rectilinear. The principle by which the steam engine becomes a moving power, is exceedingly simple; the complexity arises from the various kinds of machinery by which the force is applied to the required purpose. The history of the steam engine presents a series of the most brilliant applications of ma

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chinery which have ever been witnessed; and it is the object of this chapter, to trace the rise and progress of the invention, and to conduct the reader, by easy steps, from its simple to its complex state; from the first production of the moving power, through the subsidiary details of mechanism which have been successively introduced.

14. Hero's Machine.-The generation of steam from water by the application of heat, and the mechanical force produced by this means, appear to have been understood at a very remote period; but their application to machinery devoted to the purposes of locomotion, is a discovery of recent date. The ingenious contrivances of early discoverers were devoted to objects of minor importance, as those of raising water, of propelling smoke upwards, &c. About 120 years before the present era, an elegant machine was constructed by Hero, of Alex

andria, in which a rotatory motion was produced by means of steam. A hollow globe placed on pivots, was furnished with a number of horizontal tubes radiating from it like the spokes of a wheel, and closed at their ex

Fig. 5.

tremities, with the exception of a small orifice near the end, and on the side, of each tube. The globe being supplied with steam, this fluid rushes through the orifices with a force equal to the excess of its elasticity over that of the atmosphere. The recoil produced by this difference of pressure, repels the tubes in the opposite direction, and a rotatory motion is produced, which may be communicated to machinery connected with the globe.

15. Garay; De Caus; Branca.-A long interval ensued, during which there appears to have been no discovery in the application of steam power to locomotion. 1. In 1543, Blasco de Garay, a Spanish sea captain, invented a machine by which a vessel could be propelled without oars or sails.

MARQUIS OF WORCESTER.

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The experiment was made in the port of Barcelona, and appears to have been successful. But the nature of the apparatus, with the exception of a boiler having been employed, and wheels attached to the sides of the vessel, was concealed, and the experiment was not repeated. 2. In the early part of the next century, De Caus, a Frenchman, published a Treatise on Moving Powers and Machinery, which contained some indistinct views of the processes of evaporation and condensation, but conveyed no intelligible ideas of the elastic force of steam. He ascribed the mechanical force, occasioned by the conversion of water into steam, to the action of heat upon the air which is mixed with the water. He discovered that "water will mount by the help of fire, higher than its level;" but this process is described by him as depending on physical causes altogether unconnected with the properties of steam; the term steam, in fact, is not mentioned in his, description of his machine. 3. In 1629, Giovanni Branca, an Italian, contrived a machine which was employed for the various purposes of raising water, of sawing timber, of pounding materials, &c. His machine consisted of a wheel furnished with flat vanes around its circumference, like the boards of a paddle-wheel. Upon these vanes, steam was propelled from a close vessel. A rotatory motion was produced, and communicated to appropriate machinery.

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Fig. 6.

The results, however, of these and other discoveries made about this period, have never been rendered applicable to the purposes for which the modern steam engine is adapted.

16. Marquis of Worcester.-In 1663, the Marquis of Worcester published a work, in which he described a method of raising water to great heights by the pressure of steam. He found that the force of steam was sufficient to burst a cannon; and, under the head of a Fire Water Work, he states:-"One vessel of water rarefied by fire, driveth up

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SIR SAMUEL MORLAND.

forty of cold water; and a man that tends the work is but to turn two cocks, that, one vessel of water being consumed, another begins to force and re-fill with cold water, and so successively, the fire being tended and kept constant; which the self-same person may likewise abundantly perform in the interim between the necessity of turning the said cocks.' The nature of the machinery employed for this purpose is of less consequence to us than the fact, that an important step was here gained in the progress of invention, as, whatever apparatus was employed, the steam was generated in one vessel, and applied to mechanical purposes in another, according to the method at present adopted in steam engines. The effect produced was equivalent to raising 20 cubic feet of water one foot high, by means of one pound of coals, or about the 2000th part of the effect of a good steam engine. It is obvious that there was much loss of effect by the considerable amount of condensation produced by the contact of the steam with cold water. But the Marquis appears to have been unacquainted with the effect of condensation, and his plan of operation must consequently have been very simple.

17. Sir Samuel Morland.-In 1675, Sir Samuel Morland obtained a patent for a powerful machine, by which he was enabled to raise water from the Thames to the top of Windsor Castle, and even sixty feet higher, in a continual stream, at the rate of sixty barrels per hour. In 1683, he published a work on "The Principles of the New Force of Fire," which contains some calculations of the size of cylinders adapted for raising, by steam, a certain quantity of water, to a given height, in a minute. This work contains also an estimate of the amount of expansion of a quantity of water into vapour, which is remarkable for its approximation to the truth at this period. The machinery employed by Morland is not known. His researches appear to have had little influence on the progress of the practical application of steam, as it is employed in the present day.

A Century of the Names and Scantlings of Inventions, Art. 68.

SAVERY'S STEAM ENGINE.

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18. Denis Papin.-In 1695, Denis Papin, a Frenchman, suggested the idea of raising a piston within a cylinder by steam, and forming a partial vacuum beneath the piston by condensing the vapour, by which means the atmospheric pressure might be brought to aid the effect of his apparatus. This contrivance for producing a moving power may be fully understood, by referring to fig. 3, p. 13, and the description there given. The atmospheric pressure being equivalent to a weight of fifteen pounds on the square inch, if the piston be supposed to have a diameter of only one square foot, a power is here obtained of equal amount to a pressure of 1710 pounds. "The real authors of the atmospheric engine," observes Tredgold, "were very likely indebted to this suggestion; but neither Papin himself, nor his rival Savery, discovered how to turn this suggestion to advantage." Papin was, in fact, ignorant of the means of procuring an effective vacuum; he proposed to produce it by means of gunpowder, and afterwards by common air-pumps worked by a waterwheel; the fire was alternately applied to, and removed from, the cylinder; but the vacuum was always insufficient. Papin, however, produced a more perfect engine, after he had become acquainted with Savery's machine, which, in the order of discovery, must be next noticed.

19. Savery's Steam Engine.-Thirty years after Lord Worcester's death, Captain Thomas Savery constructed an engine, in which the force of steam is employed as a moving power for raising water. He appears to have discovered the principle of condensation by chance. Having drunk a flask of Florence wine, and thrown the flask on the fire, he called for a basin of water to wash his hands. He observed that a small quantity of wine remaining in the flask began to boil, and that steam issued from the flask. He then seized the vessel, and plunging its mouth under the surface of the water in the basin, found that the liquid rushed into the flask. This experiment suggested to him the possibility of producing a vacuum by the condensation of steam, and bringing the atmospheric pressure to bear upon the vacuum thus pro

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