Chap. 6.]
Liquids of different Specific Gravities.
519
No. 237 (the first figure in the Spiritalia) represents an ordinary siphonresting over the handle of a vase, within which the short leg is inserted.This instrument was charged by sucking, as the more ancient ones in thelast cut.
No. 238 exhibits another form of the siphon, consisting of two straightand separate tubes, the smaller one of which is inserted through the bot-tom of the covered vase, and reaches as high within it as the liquid isrequired to stand. Over this tube another one is slipped wbose upperend is closed air-tight. Hence it is obvious that when the liquid is higherthan the orifice of the inner tube which forms the long leg, it will ascendbetween the tubes and continue to be discharged as in the common siphon,until the surface descends below the lower end of the outer tube, or shortleg. Here the liquid is discharged from the bottom of the vessel, notover its rim as in the preceding figure. The siphon admits of a greatvariety of modifications, some of which in the hands of ancient jugglerscontributed not a little to amaze the ignorant. The Contents of the largevases, often permanently fixed in temples, could and doubtless often weresecretly emptied by contrivances of this kind ; the siphons of course beingconcealed in the Ornaments , handles, or other adjuncts. The six vesselsof wine placed daily in the temple of Bel, which the priests clandestinelyemptied every night, might have been more neatly robbed of their contentsby concealed siphons, than by entering through a secret passage under thealtar ,• but as the abstraction of the more solid food which the priests pre-tended was consumed every day by the brazen deity, (forty sheep andtwelve measures of floor,) required some contrivance like the latter; thevases were emptied at the same time. [Story of Bel and the Dragon .]The romantic account by Herodotus of the robbery of Rhampsinitus ’ trea-sury, shows to what extent the System of secret passages was carried, andthe ingenuity with which they were made and concealed.
The velocity with which water flows from an ordinary siphon necessarilydiminishes as the surface in the reservoir falls. In some cases a uniformdischarge is desirable. No. 239 shows how ancient engineers accomplishedthis. A float or hollow dish was attached to the end of the short leg, sothat the instrument descended with the water. The long leg was passedloosely through two openings in projecting pieces that preserved it in theproper position.
The difference in the specific gravity of liquids was a fruitful sourceof deception. Many Capital tricks were based upon it, especially whenthe lighter fluids employed were of the same color as those on which theyreposed. If for example, a vessel contained oil, wine and water, theseliquids oould be discharged by a siphon like No. 239 in the same Order;and by secretly raising or lowering an ordinary one, or the moveable tubein No. 238, any one liquid could be drawn off. Fresh water being lighterthan salt is often found some distance at sea ; and sailors, like old jugglers,can draw up either, according to the depth to which their buckets areimmersed. Four miles from the mouth of the Mississippi the fresh wateris about two feet deep, and at ten miles it may be obtained by carefuldipping.
In problem XXX of the Spiritalia, Heron shows how siphons may beconcealed within the figures of oxen or other animals in the act of drink-ing ; the orifice of the short leg being at the mouth, and that of the longone in one of the feet. See No. 240. When the bore of the siphon isproperly adjusted to the quantity of water flowing into a basin, the animalwill appear to drink the whole.