HYDRAULICS. 
action, and in the same time, that which 
has the greatest altitude must have the 
greatest scope of action, and move with an 
increased velocity in exact ratio with the 
difference of the diameters. When the ve- 
locity of the machinery attached to the 
movement-tube is to be diminished, with- 
out losing the height to which the secondary 
power is thus raised by the additional length 
of the tube, the segment on which it is 
made to act must be that of a larger cir- 
cle, as shewn in fig. 4, where the tube, A B, 
is of double the diameter of that at C D, 
which would raise the lever, E, to the height 
F. N ow, if this lever were the handle of 
a pump, requiring a considerable exercise 
of power, it is evident the fulcrum, G, must 
be placed very near to the pump-tube, H ; 
whereby the radius of the circle, G F, is 
greatly increased, and the plonge of the 
pump-piston, H, much diminished. If, on 
the contrary, the fulcrum had been at O, 
i. e. dividing the distance between D and 
X into three parts, of which two are given 
to the lever, N, the plonge would be fat- 
deeper, but the power would be greatly 
reduced ; the segment, D F, occupying a 
greater angle with the fulcrum O, than it 
does with the fulcrum G. This is amply 
explained under the head of Mecha- 
nics. 
Where water is enclosed within a vessel, 
or in a tube, in such manner that air cannot 
penetrate, it will not flow out in the same 
manner as if air were admitted to supply 
the place of any quantity that might be 
required to be drawn off. Of this every 
person must be sensible who lias ever at- 
tempted to draw wine, beer, &c. 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 disposition to gravitation, they 
are perfectly inelastic, if they were other- 
wise, 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 ta- 
ken to draw off liquors from one vessel to 
another, by means of a very simple instru- 
ment, called a syphon. This is a pipe of 
tin, copper, &c. according to its purpose, 
bent at any angles but generally about 70 
to 80 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 ves- 
sel. See fig. 5, in which the syphon, 
ABC, is inserted into a vessel to be emp- 
tied. 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 operator inhales 
forcibly, and by thus drawing the air out of 
the syphon, causes the liquor to rise in it* 
place. The absence of air, which first 
caused the fluid to ascend into the tube, 
occasions it to remain until the finger is 
removed from the end, A ; when die pres- 
sure of the air within the vessel causes the 
liquor to press through the syphon, which 
continues to the last to draw off the con- 
tents of the vessel, they pressing forward 
through the long end, A. It is proper to 
remark, that large syphons sometimes re- 
quire to be previously filled, and then to be 
set in the vessels to be drawn off; but, in 
general, the casks, &c. can be tilted suffici- 
ently to answer this purpose, and to bring 
the shorter limb nearer to a horizontal posi- 
tion than the longer limb, whereby the lat- 
ter may 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 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 perpendicular height is 
equal to the weight of the atmosphere press- 
ing on the surface of such a column, it fol- 
lows that no syphon exceeding that length 
w ill 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 perpe- 
tual hunger and thirst, amidst a profusion 
of delicacies, which always receded when 
applied to his lip. To imitate this disap- 
pointment, a syphon, having its two limbs 
parallel and contiguous, is fixed into the 
middle of a cup double its height; one 
limb receiving the liquid at the bottom of 
the interior, and the other discharging it 
