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[Book IV.
appears from one of the Hamilton Vases, that large bellows were some-times used to promote the combustion by a blast.
A modern mechanician will at once perceive that the radiation of heatfrom such fires into the interior of altars offered an effective and unsuspi-cious source of fraud—one from which a distinct series of prodigies mightbe derived. Let us see how they could be realized. Suppose a bronzealtar made air-tight, with a cylindrical or other opening through its centre,in which to place the fire and to afford a draft, (as in those wooden boilersin which water is heated by a fire in the centre ; the liquid being in con-tact with the heated sides of the furnace, and the ashes from the gratefalling through the draft opening, which is continued through the bottomof the boilers) or the passage for the draft might be made at right anglesto the furnace or fire-place, and terminate at one side of the altar; the up-per part of the furnace would then be level with the top of the altar uponwhich the victim was laid. Suppose the air-tight cavity round the fur-nace filled to a certain height with wine, oil, or other inflammable liquid,a vapor would then be evolved by the heat, and mixing with the contain-ed air would press upon the surface of the liquid, which, by concealedtubes might be conveyed to the fire and thus sustain it without any addi-tional fuel. The vapor might also be made to produce sounds as in Dreb-ble’s machine—images of birds might by it be made to sing—dragonsand serpents to hiss. The current, like the blast of a bellows, might bemade to excite the flames ; and by appropriate mechanism impart motionto various automata—cause the doors of the temples mysteriously to flyopen and to close, &c. &c. Now it so happens that these very thingswere done and by means of air and vapor.
The annexed figure, from Problem XI, of the Spiritalia, will serveas a specimen of the ingenuity of the ancients in these respects. It ismerely one of a number that Heron has given. The altar was of metal,hollow and air-tight, and placed on a hollow base or pedestal (also air-tight) which contained a quantity of oil or wine. Upon the base stood
two statues, each holding a vase inone hand as represented. ^ Pipes, asshown by the dotted lines, communi-cated through the statues with theliquid. As the air within the altar be-came dilated by the heat, it necessarilyforced the liquid up the pipes anddrove it out of the mouths of the va-ses in which the pipes terminated. Itis not easy to see why the bottom ofthe altar did not open directly into thebase or reservoir of wine, instead ofthe pipe that connects them, since itwould have promoted the evolutionof vapor; büt the figure representsonly one of the nümerous modifica-tions employed. It is obvious from this and some other devices describedby Heron , (as No. 173) that vapor from the contained liquids contributedchiefly to the result, although he has not in all cases mentioned it. Indeedit is not certain that he did not confound steam with air, as the philoso-phers of the sixteenth Century did, of which some examples are givenin the next two chapters. Had air alone been used in the above altar,the effect could only have have been momentary ; for part of it wouldbe soon absorbed by the liquid and carried out with it, and there appears