394 Eolipiles. from Herrn. [Book IV.

this last being always kept filled by a pipe from the aqueduct or castel-lum. Remains of the pipes, cocks, copper flues, &c. have been found inabundance, but the details of the heating apparatus and those connectedwith the elevation and distribution of the liquid have not been ascer-tained : this is to be regretted because, from the number and magnitudeof the hot baths at Rome , the operations of boiling and dispersing thewater must have been conducted on a scale far more extensive than anything in modern times—the most extensive breweries and distilleriesnot excepted. Some idea of the operations may be derived from the factthata single establishment could accommodate two thousand persons withwarm, or rather hot, baths at the same time. Seneca, in a letter to Luci-lius, says “ there is no difference between the heat of the baths and aboiling furnace and it would, he observes, appear to a reasonable manas a sufficient punishment to wash a condemned criminal in them. Thepersons who had the Charge of heating in close vessels and distributingdaily such large quantilies of water, must necessarily have been conver-sant with the mechanical properties of steam, and with economical modesof generating it. In some cases the water was heated by passing througha coiled copper tube, like a distiller’s worm, which was embedded in fire.We have previously remarked that the Romans also heated water bymaking it pass through the hollow grates of a furnace. (See Pompeii,vol. i, 196, and G-ell’s Pompeiana.)

Besides the various applications of heated air and of vapor alreadynoticed, there is in problem XLV of Heron’s Spintalia, a description ofa close boiler, from the upper part of which a current issues that Supportsat some distance above the boiler a light ball like those that are made toplay on jets of water. (See the annexed figure, No. 179.) The whir-ling eolipile, No. 180, is the subject of problem L—and is the earliestrepresentation of a machine moved by steam that is extant. It consists

of a small hollow sphere, fromwhich two short tubes proceedin the line of its axis, and whosaends are bent in opposite direc-tions. The sphere is suspend-ed between two columns, theirupper ends being pointed andbent towards each other. Oneof these columns was hollow andconveyed steam from the boilerinto the sphere, and the escapeof the vapor from the smalltubes by its reaction imparted arevolving motion to the sphere.These two applications of steamhave been considered the resultof a fortunate random thought,which Heron, or some other oldmechanic, stumbled on by a species of chance medley, whereas they cer-tainly mdicate an intimate though it may be a limited acquaintance withthe mechanical properties of that fluid. We should never suppose thatthis elegant application of the jet to sustain a ball in the air was the fruitof a first attempt to use steam, much less that the complex movement ofthe whirling eolipile was another thought of the moment. Did anymodern experimenter m hydraulics ever hit upon the Suspension of a ballby a jet of water in his first essays, or devise Barker’s mill at a sittmg,

Eolipiles, from Heron.

No. 179.

No. 180.