374

Machines for Raising Water hy Fire.

[Book IV.

CHAPTER II.

Machines for raising water by fire: Air machines—Ancicnt weather-glasses—Dilatation of air by heatand condensation by cold—Ancient Egyptian air-machines—Statue of Memnon—Statues of Serapis an$the Bird of Memnon—Decaus’ and Kircher’s machinery to account for the sounds of the Theban Idol—

Remarks on the Statue of Memnon—Mttchine for raising water by thesun’s heat, from Heron_Similar

machines in the sixteenth Century—Air-machines by Porta and Decaus—Distilling by the sun’s heat- Mu-sical air machines by Drebbie and Decaus—Air machines acted onby ordinary fire—Modifications of thememployed in ancient altars—Bronze altars—Tricks performed by the heathen priests with fire—Othersby heated air and vapor—Bellows empjoyed in ancient altars—Tricks performed at altars mentioned byHeron—Altar that feeds itself with Harne, from Heron—Ingenuity displayed by ancient priests—Secretsof the temples—The Spiritalia—Sketch of its eontenls—Curious Lustral Vase.

A separate book might with propriety have been devoted to machineswhich raise water through tabes by means of the weight, pressure, mo-mentum, or other natural properties of liquids, without the necessary in-tervention of wheels, cranks, levers, &c. With such, those now to bedescribed might also have been classed, since they too require neitherexternal machinery nor force. They differ however from pressure-engines and water-rams, and every other device yet noticed, in bringinginto action a new elenjent, viz. heat or fire. It is by this that the forceupon which their movements depend is geixerated, viz. in the expansionof elastic fluids. There are two kinds of these machines which differ ac-cording to the fluid medium upon which the fire is made to act. In somethis is common air, in others stearn or vapor of water, and sometimes bothsteam and air have been employed. The present chapter is appropriatedto air machines. These might be divided into two classes, according tothe nature of the heat employed; in some this is derived from the sun;in others, from ordinary fire. Those in each dass might also be arrang-ed according to that properfy of the air upon which their action depends,viz. 1. the force developed by its expansion ; 2. the vacuum formed by itscondensation ; 3. those in which both are combined. The first might becompared to forcing pumps, the second to sucking or atmospheric ones,and the third to those which both suck and force up the water.

It was observed in the second book (page 176) that all gases or airsare expanded by heat and contracted by cold. A pr.oof of this is affordedby the usual mode of employing cupping-glasses ; a minute piece of cot-ton or sponge dipped in alcohol js infiamed and placed in a glass; uponwhich the air becomes dilated or increased in bulk, so that a great part,is driven out to make room for the rest; the mouth of the instrument isthen applied to the place from which blood is to be withdrawn; the flame ofthe cotton is thereby extinguished and as the remaining air becomes coolit cannot resume its previous state of density, and consequently a vacuityor void is left in the glass. Plumbers sometimes make small square boxesof sheet lead ; and on soldering in the covers the temperature of thecontained air is so greatly increased, that before the soldering is completeda large portion is expelled, and when the boxes become cool every sideis found slightly collapsed. This result is the required proof of the ves-