39 5
Chap. 3.
without having ever heard of either? No more than any old mechanicianever invented the above before experimental researches on steam had be-came familiär to him, if not to his contemporaries. Besides, there havebeen within tbe last half Century not less than half a dozen patents takenout for rotary steam engines identical in principle with the whirlingeolipile. The fact seems to be that Heron selected the two devicesabove, on the same principle as the rest of the illustrations, i. e. such asin his judgment would be the most interesting.“
From a remark of Vitruvius in the first book of his Architecture, chap. 6,\ve learn that those portable steam machmes named Eolipiles, (from Eolusthe god of wind, and their application to create artificial winds) were incommon use in his time. Speaking of the town of Mytilene , he observesthat the inhabitants were subject to colds, in those seasons when cer-tain winds blew; and which might have been in some degree avoidedby a more proper disposition of the streets. “ Wind, [he remarks] is onlya current of air, flowing with uncertain motion;—it arises from the actionof heat upon moisture—the violence of the heat forcing out the blasts ofair. That this is the fact, the brass eolipiles make evident ;—-for the op-erations of the heavens and nature may be discovered by the action ofartificial machines. These brass eolipiles are hollow and have a very nar-row aperture, by which they are filled with water, and then placed on thefire :—before they become hot, they emit no efjluvia, but as soon as the waterbegins to boil, they send forth a vehement Mast.” As these instrumentshave been adapted to a great variety of purposes, as well as being inti-mately connected with this part of our subject, we shail notice them withsome detail. From the times of Vitruvius to those of Des Cartes , and upto the present Century, they have been used as philosophieal Instrumentsto illustrate the nature of winds and meteors, as well as for other scien-tific pursuits. They were used as Substitutes for bellows in blast furna-ces and ordinary fires. The draft of chimneys was increased by meansof them. They were made to produce music and disperse perfumes.They constituted the distilling vessels of the alchymists, and in anotherform were employed as weapons of war, and were even deified in thesteam idols of old. They were the first instruments employed to raisewater by steam, and the first to produce motion by it; and hence theyconstitute the germ of modern steam engines, to which we may add thatthey led to the invention of steam guns. (See Martin’s Philosophy, vol.n, 90.) They are commonly made of iron, brass, or strong copper, hav-ing a short neck in which a very minute opening is made. In Order toCharge one with water (or other liquid) it is placed on a fire until nearlyred hot; it is then taken off, and the neck placed in water or the wholeplunged in it, which, as the vessel cools, takes the place of the air drivenout by the heat. It is then placed on a brazier of charcoal or other fireuntil steam is rapidly evolved and discharged with violence at the orifice.
Vitruvius has not mentioned the particular purposes for which eolipileswere used by the Romans. It is however known that they were em-ployed as bellows for exciting fires; and as this was not for want of thelatter instruments, they must have had properties which rendered them
“ Balls daneing on jets of water and air, were a favorite accompaniment of the oldgarden water works, and hydraulic organs, &e. of Italy , where the device has probablybeen in use since the times of the Republic : the amusement of children with peas onthe ends of tobacco pipes or reeds is in imitation of it: the current of air blownthrongh the perpendicular tube keeps the tiny globe some inohes above the orifice,where its motions, varying with the force of the current, produce a very agreeable■effect.