378
Air Machine — From, Herrn.
[Book IV.
the adjoining ternple. The Romans do not appear to have had sufficientcuriosity to give it a critical examination. What a contrast it forms wit.hsome modern wonders ! These have puzzled people only while exami-nation was prohibited—while access to them was denied, as the chess-player of Kempelen ; but the colossal android of Thebes defied the scruti-ny of the world through unknown periods of time. In it, the old priestsof Egypt have sent döwn a surprising specimen of their skill. We knowfrom the Bible that they had a profound knowledge of Natural Magic;i. e. of the applications of Science to purposes of deception, and this Statue ■confirms the scriptural account:—it shows us what an amount of laborand ingenuity was expended in the fabrication of idols, and to what aprodigious extent the ancient Systems of delusion were carried—how thevery magnitude and even sublimity of the impostures were calculated tobear down the intelleet and establish an unshaken belief in the communionof the priests with the gods.
If a close metallic vessel containing water be exposed to the sun, theair in the upper part will become dilated by the heat and may be employ-ed to raise the water : for if a tube be inserted at the top, and the lowerend reach nearly to the bottom, the elasticity of the air will be expended inforcing the liquid up the tube and to an elevation according to the increaseof its temperature. A device of this kind is described by Heron whichis represented in the annexed cut.
On the lid of a box or cis-tern containing water is placeda globe, also partly filled withthe same fluid. A pipe risesfrom the cistern to about thecentre of the globe. Anotherpipe through which the wateris to be raised proceeds fromnear the bottom of the globeand terminates over a vase orcup, which communicates withthe cistern as represented.When .the sun beams fall onthe globe, the air within is ra-refied and by its expansionforces the .water through thepipe into the vase, throughwhich it descends again intothe cistern. When the sun beams are withdrawn and the surface ofthe globe becomes cool, a partial vacuum is formea in the globe, and thepressure of the atmosphere then drives a fresh portion into it from thecistern below ; when it is again ready to be acted on by the sun as before.In addition to the air, at first contained in the globe, a quantity of vaporor low steam would be evolved by the heat and contribute greatly to theresult. The cistern represents an open reservoir which may be at a dis-tance from the globe, and the vase merely exhibits the place of discharge—having no necessary connection with the reservoir. The apparatus asa model, is figured just as philosophical instruments still are. Thus inmodern books, a pump (for example) is often shown as discharging waterinto the reservoir from which it raises it. We make these remarks be-cause some persons are too apt to consider these ancient figures as literalrepresentations of working machines, whereas, they were designed merelyto illustrate the principles upon which the movements depended; and as
i liiilllllllllirP
yfi,;; i