Plate XCIX.—Hydrostatics.—Fig. 8. Cup of Tantalus.details

Tantalus’s cup.

Let a hole be made quite through the bottom of the cup A (fig. 11) and the longer leg of the bended syphon BCED be cemented into the hole, so that the end D of the shorter leg DE may almost touch the bottom of the cup within. Then, if water be oured into this cup, it will rise in the shorter leg by its upward pressure, extruding the air all the way before it through the longer leg: and when the cup is filled above the bend of the syphon at F, the pressure of the water in the cup will force it ocer the bend of the syphon: and it will descend in the longer leg CBG, and run through the bottom, until the cup be emptied.

This is generally called Tantalus’s cup, and the legs of the syphon in it are almost close together; and a little hollow statue, or figure of a man, is sometimes put over the syphon to conceal it; the bend E being with the neck of the figure as high as the chin. So that poor thirsty Tantalus stands up to the chin in water, imagining it will rise a little higher, and he may drink; but instead of that, when the water comes up to his chin, it immediately begins to descend; and so, as he cannot stoop to follow it, he is left as much pained with thirst as ever. (p. 808)