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HERO'S INVENTIONS.

11 On the lid of a box (fig. A*) or cistern, a, containing water, Hero places a globe, c, also partly filled with the same fluid; a pipe, e, rises from the cistern into the globe. Another pipe, i, proceeds from the globe, terminating over a vase, m, and the vase itself communicates with the cistern by a pipe, n.

When the sunbeams fall on the globe, they heat the water, and raise vapour; this, by its expansion, forces the water through the syphon, i, which, trickling into the vase, m, is again conducted by the pipe, n, placed within it, into the cistern. When the sunbeams are withdrawn, and the surface of the globe cooled by the ambient air, the vapour within is condensed, and by this means a vacuum is left in its upper part; the pressure of the atmosphere now forces the water in the cistern up the pipe, e, to replenish it, and the same operation of forcing water commences when the sun's rays, falling on the surface of the globe again, heat its contents.

Here, almost under any circumstances, the effect could have been but trifling; but in the second, (fig. B,t) where the heat from a lamp, or

"47. Quæ gutta appellatur, stillat sole in ipsam ingruente. Sit basis præclusa per quam infundibulum impellatur, cujus caulis à fundo paululum distet: et sit sphærula ex qna tubus in basim feratur, a fundo vasis, et à pariete sphærulæ parum distans. Inflexus autem siphon sphærulæ aptatus feratur in infundibulum, et in sphærulam aqua injiciatur. Quando igitur sole in sphærulam ingruit, calefactus aër existens in ipsa humidum expellit. Quod quidem fertur per siphonem et per in. fundibulum in basim procedit sed cum sphærula obumbrata fuerit excedente aëre, tubus, qui ducitur per sphærulam humidum assumet, et locum exinanitum replebit. Atque hoc toties erit, quoties sol in ipsam ingruet.”. p. 63. Heronis Spiritalium Liber a Commandino. Amst. 1680.

† “ 45. Et sphæræ trepudiant hoc modo. Lebes aquam habens cooperto ore succenditur. Ab operculo autem procedit tubus, ex cujus dimidia sphæra concava simul perforatur. Si

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HERO'S STBAM MACHINES. from a fire, is substituted in the place of that proceeding from the sun, the power would not only be more available, but less hypothetical.

A caldron or vase, a, has a pipe, c, inserted into its lid, formed at its upper end like a small cup, i, and containing a ball or hollow sphere, 0. A fire being made under the boiler, the steam, rising from the water which it contains, flows through the pipe, and lifts up the ball placed in the basin, and keeps it suspended in the air as long as the vapour rises with the proper velocity from the caldron.

A motion round an axis is elegantly given, (fig. C,*) to a small globe, by means of the reaction of steam upon the air. Two pipes, a, c, each having their upper extremity bent towards each other, rise from the cover of a vase, o; one of these, c, acts merely as a pivot, the other, a, conducts steam, raised in the boiler, into the ball or globe, i. This is suspended between them by having the steam-pipe, a, inserted into it, and is kept in its position by the pivot formed at the end of the opposite pipe, c. Two pipes, m, n, also bent at right angles at their extremities, are inserted into the circumference of the globe, and HERO'S STEAM MACHINES.

igitur levem sphærulam in dimidiam sphæram injiciamus, continget vaporem, qui ex lebete per tubum attolitur, sphæru. lam elevare adeo ut tripudiare videatur." p. 62. Ibid.

* “50. Lebete succenso sphærulam ad cnodacem moveri. Sit lebes succensus, qui aquam habeat obstruaturque osculum cooperculo: et unà cum eo simul perforetur tubus inflexus cujus extremitas concavum sphærulam aptetur. Extremitate autem ex diametro opponatur cnodax cooperculo nixus : et sphæra duous tubulos inflexos habeat secundum diametrum simul cum ipsa perforatus, qui vicissim infectantur: sint que inflexiones ad rectos ungulos continget igitur succenso lebete vaporem per túbum in sphæram incidentem extra cadere per tubos inflexos, et sphæram convertere, quemadmodum in ani. malibus choreas ducentibus." p. 66, Ibid.

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form a communication between the caldron and the atmosphere.

Heat being applied to the caldron, the steam, flowing from it through the vertical pipe a, into the litile globe, i, thence finds its way through the pipes or arms, m, n, into the atmosphere ; at this instapt the reaction of the vapour on the air makes the globe revolve with a magical celerity,

as if it were animated from within by a living spirit."

These three attempts at employing steam as a mechanical power are described, without even a hint at their extension to any useful purpose. This can detract but little from the merit of Hero; a sagacity little short of prescience could alone have enabled him to anticipate the grandeur of that creation that was to arise from these beautiful but comparatively insignificant beginnings.

That so ingenious a people as the Greeks should not have been led, by those direct experiments, to a practical application of the agent, so exquisitely moulded by Hero into a mechanic power, may, in all probability, be ascribed to the operation of the same causes as those which have thrown a veil of deep and impenetrable obscurity on so many of the arts of antiquity. “ The ancient philosophers,” says an excellent mechanic, “ esteemed it an essential part of learning to be able to con. ceal their knowledge from the uninitiated ; and a consequence of their opinion, that its dignity was lessened by its being shared with common minds, was their considering the introduction of mechanical subjects into the regions of philosophy a degradation of its noble profession; insomuch, that those very authors among them, who were most eminent fortheir inventions, and were willing, by their own practice, to manifest unto the world

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ANTHEMIUS AND ZENO. these artificial wonders, were, notwithstanding, so infected by this blind superstition, as not to leave any thing in writing concerning the grounds and manners of these operations; by which means it is that posterity hath unhappily lost, not only the benefit of these particular discoveries, but also the proficiency of these arts in general. For when once learned men did forbid the reducing them to vulgar use and vulgar experiment, others did thereupon refuse those studies as being but empty and idle speculations; and the divine Plato would rather choose to deprive mankind of those useful and excellent inventions, than expose the profession to the ignorant vulgar.”

The love of ingenious and refined contrivance, which, notwithstanding the neglect of their philosophers, may be said to have formed a prominent feature in the character of the Greeks, descended not, along with their empire, to the Romans. Improvements in the arts are sought for in vain among these victorious soldiers, during the rise and progress of their iron power; a solitary instance of an application of steam is all that can be gleaned from the historians who described its decline and fall.

“ In a trifing dispute between Anthemius, the architect of Justinian, and Zeno the orator, relative to the walls or windows of their contiguous houses, Anthemius had been vanquished by the eloquence of his neighbour Zeno; but the orator was defeated in his turn by the master of mechanics. In a lower room, Anthemius ranged several vessels or caldrons of water, each of them covered by the wide bottom of a flexible tube, which rose to a narrow top, and was artificially conveyed among the joists and rafters of the adjacent buildings; a fire was kindled beneath the caldrons; the

ANTHEMIUS AND ZENO.

15 steam of the boiling water ascended through the tubes; the house was shaken by the effort of the imprisoned air, and its trembling inhabitants might wonder that the city was unconscious of an earthquake they had felt; and the orator declared in a tragic style to the senate, that a mere mortal must yield to the power of an antagonist, who shook the earth with the trident of Neptune.”

The centuries of turbulence which succeeded, were unfavourable to genius of every kind; useful things were disregarded, because they were common; mystery pervaded every pursuit; inventions could be learnt only by deciphering anagrams; and those contrivances were valued highest for their ingenuity, the principle of which could be the most carefully concealed. In this unfortunate direction given to inquiry, we cease to wonder at the small progress which was made, or that centuries should pass away without a mite being added to the scanty stock of me chanical invention. An organ, described as an object of wonder in the early part of the twelfth century, will not furnish an exception. It shows only that a problem in the “ Pneumatica” was resolved with skill even by one of the schoolmen.

About the year 1125, according to the relation of William of Malmsbury, " there were extant in a church at Rheims, as proofs of the knowledge of Gerbert, a public professor in the schools, a clock, constructed on mechanical principles, and an hydraulic organ, in which the air, escaping in a wonderful manner by the force of heated water, fills the cavity of the instrument, and the brazen pipes emit modulated tones through multifarious apertures."

On the revival of learning in Europe, the ancient Platonic contempt of experiment may be said to

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