HYDRAULICS. 



anight be required to be drawn off. Of 

 this every person must be sensible who 

 has ever attempted to draw wine, beer, 

 fee. from a full cask, without opening a 

 vent at the top, near the bung, to admit 

 air, as the fluid might evacuate the upper 

 part of the vessel From this we prove, 

 that although all fluids have a direct dis- 

 position to gravitation, they are perfectly 

 inelastic ; if they were otherwise, we 

 should find that, by expansion, they would 

 be capable of filling a greater or lesser 

 space at times ; and that as the wine, &c. 

 were drawn off below, the portion re- 

 maining in the vessel would expand, and, 

 though less dense, would fill the whole 

 interior. 



Of this property advantage has been 

 taken to draw off' liquors from one vessel 

 to another by means of a very simple in- 

 strument called a syphon. This is a pipe 

 of tin, copper, &c. according to its pur- 

 pose, bent at any angle, but general- 

 ly about seventy "to eighty degrees, in 

 such manner that one limb may reach 

 down through the bung-hole of the cask 

 to be emptied, to its very bottom ; the 

 other leg should be the longest, so that 

 when filled it may contain a heavier body 

 of fluid than that limb within the vessel. 

 See fig. 5. in which the syphon, ABC, 

 is inserted into a vessel to be emptied. 

 In large syphons it is necessary to insert 

 a cock at the lower end, to prevent 

 the escape of the fluid when first filled. 

 In small syphons it is common to put a 

 small parallel tube, which being applied 

 to the mouth, the end C, being immersed 

 in the liquor to be drawn off, the opera- 

 tor inhales forcibly, and by thus drawing 

 the air out of the syphon, causes the li- 

 quor to rise in its place. The absence 

 of air, which first caused the fluid to as- 

 cend into the tube, occasions it to remain 

 until the finger is removed from the end 

 A ; when the pressure of the air within the 

 vessel causes the liquor to press through 

 the syphon, which continues to the last 

 to draw off the contents of the vessel, 

 they pressing forward through the long 

 end, A. It is proper to remark, that large 

 syphons sometimes require to be previ- 

 ously filled, and then to be set in the ves- 

 sels to be drawn off; but, in general, the 

 casks, &c. can be tilted sufficiently to an- 

 swer this purpose, and to bring the short- 

 er limb nearer to a horizontal position 

 than the longer limb, whereby the lat- 

 ter my possess a greater perpendicular 

 altitude, and consequently a greater ten- 

 dency to gravitation. For we trust, that, 

 in Fig. 1, it has been demonstrated, that 



VOL. VI. 



the pressure of a fluid is in proportion 

 to its perpendicular height We must 

 caution the reader, that as a column of 

 water of thirty -three feet in perpendicu- 

 lar height is equal to the weight of the 

 atmosphere pressing on the surface of 

 such a column, it follows, that no syphon 

 exceeding that length will act, because 

 the power would be less than the weight 

 to be raised. 



A comical display of the properties of 

 the syphon is seen in what is called 

 " The cup of Tantalus ;" the designation 

 of which is derived from fabulous history, 

 wherein we are told, that Tantalus, king 

 of Phrygia, was condemned by Jupiter to 

 suffer perpetual hunger and thirst, amidst 

 a profusion of delicacies, which always 

 receded when applied to his lips. To 

 imitate this disappointment, a syphon* 

 having its two limbs parallel and contigu- 

 ous, is fixed into the middle of a cup dou- 

 ble its height; one limb receiving the li- 

 quid at the bottom of the interior, and the 

 other discharging it through the centre 

 of the bottom, as seen in fig. 6. Thus, 

 when the outlet is stopped by means of a 

 finger applied thereto, the cup may be of- 

 fered quite full to the person on whom 

 the joke is to be practised, observing that 

 the syphon will not act until the liquor in 

 the cup exceeds the level of its bend, 

 when the whole will be drawn through 

 the tube. This whimsical contrivance is 

 rendered yet more diverting, by having 

 the syphon so contrived, that its action 

 may commence only when the cup is in- 

 clined a little, as is usual when a person is 

 about to drink ; and if only a small flower, 

 &c. be at the bottom of the vessel, appear- 

 ing merely as an ornament, but allowing 

 the liquor to pass under its petals, Stc. in- 

 to a tube made through one of two hand- 

 les, and brought under the bottom. 



Many springs are derived from natural 

 syphons, existing in the sides of moun- 

 tains, &c. at various depths, and to vari- 

 ous extents. Some springs, situated on 

 the tops of hills, near to large ones, sup- 

 ply water all the year, others only peri- 

 odically, when they usually flow in pro- 

 fusion. In either case, the ignorant mul- 

 titude rarely attribute the supply to the 

 proper cause. We shall demonstrate 

 from whence it originates. 



When various caverns, in which water 

 is either pent up or received, lay in a re- 

 gular descent, one below the other, the 

 water will naturally pass from one to the 

 other, and cause a regular flow, more or 

 less abundant, according as the source 

 may be more or less abundantly supplied. 

 Cc 



