213 



FLUENT FLUIDITY. 



had risen among the eight cantons which, at that 

 time, composed the Swiss confederacy. It was sus- 

 pected that the booty taken from the Burgundians, 

 defeated a short time previous at Nancy, had not 

 been faithfully divided ; the larger aristocratic 

 towns made common cause, ar.,1 wished to receive 

 Freyburg and Soieure into the confederacy, to which 

 the smaller democratic cantons were opposed. An 

 assembly of the deputies of the confederate cantons, 

 which was held at Stantz (the capital of the canton 

 of Untenvalden), in 1481, for the purpose of taking 

 these affairs into consideration, was agitated by the 

 most violent debates. The dissolution of the con- 

 federacy, and, with it, the ruin of the liberty of 

 Switzerland, which must have been the inevitable 

 consequence, seemed at hand. At this crisis, bro- 

 ther Claus, as Nicholas was now called, appeared in 

 the assembly of the deputies. His great reputation, 

 his lofty and dignified appearance, which seemed to 

 bespeak a messenger from heaven, his conciliating 

 but powerful language, in which he painted the dan- 

 gers of separation, and exhorted to union, produced 

 such an impression on the assembly, that a compact, 

 famous in Swiss history as the covenant of Stantz, 

 was immediately entered into (Dec. 22, 1481) ; all 

 differences were composed. Freyburg and Soieure 

 were received into the confederacy, and the liberty 

 of Switzerland was saved. Brother Claus, after 

 having completed this work, returned, amidst the 

 blessings of his fellow citizens, to his cell, where he 

 continued teaching virtue and wisdom, till his death, 

 May 22, 1487, at the age of seventy years. All 

 Unterwalden followed his body to the tomb, and all 

 Switzerland mourned his death; foreign princes 

 honoured his memory ; and, in 1671, Clement X. 

 caused him to be beatified. 



FLUENT, in fluxions ; the flowing quantity, or 

 that which is continually increasing or decreasing, 

 whether line, surface, solid, &c. See Calculus. 



FLUID, in physiology ; an appellation given to 

 all bodies which yield, without separation, to the 

 slightest pressure, easily move among themselves, 

 and accommodate themselves to all changes of posi- 

 tion, so as always to preserve a level surface. All 

 fluids, except those in the form of air or gas, are 

 incompressible in any considerable degree. All 

 fluids gravitate or weigh in proportion to their 

 quantity of matter, not only in the open air, or in 

 vacua, but in their own elements. Although this 

 law seems so consonant to reason, it was supposed 

 by ancient naturalists, who were ignorant of the 

 equal and general pressure of all fluids, that the com- 

 ponent parts, or the particles of the same element, 

 did not gravitate or rest on each other ; so that the 

 weight of a vessel of water, balanced in air, would 

 be entirely lost when the fluid was weighed in its 

 own element. The following experiment seems to 

 leave this question perfectly decided : take a common 

 bottle, corked close, with some shot in the inside to 

 make it sink, and fasten it to the end of a scale 

 beam ; then immerse the bottle in water, and balance 

 the weight in the opposite scale ; afterwards open 

 the neck of the bottle, and let it fill with water, 

 which will cause it to sink ; then weigh the bottle 

 again. Now it will be found that the weight of the 

 water which is contained in the bottle is equal to the 

 difference of the weights in the scale, when it is 

 balanced in air ; which sufficiently shows that the 

 weight of the water is the same in both situations. 

 As the particles of fluids possess weight as a common 

 property of bodies, it seems reasonable, that they 

 should possess the consequent power of gravitation 

 which belongs to bodies in general. Therefore, 

 supposing the particles which compose fluids to be 

 equal, their gravitation must likewise be equal ; so 



that in the descent of fluids, when the particles are 

 stopped and supported, the gravitation being equal, 

 one particle will not have more propensity than 

 another to change its situation ; and, after the 

 impelling force has subsided, the particles will 

 remain at absolute rest. From the gravity of fluids 

 arises their pressure, which is always proportioned 

 to the gravity. For if the particles of fluids have 

 equal magnitude and weight, the gravity or pressure 

 must be 'proportioned to the depth, and equal in 

 every horizontal line of fluid ; consequently, the 

 pressure on the bottom of vessels is equal in every 

 part. The pressure, of fluids upwards is equal to the 

 pressure downwards, at any given depth. For sup- 

 pose a column of water to consist of any given 

 number of particles, acting upon each other in a 

 perpendicular direction, the first particle acts upon 

 the second with its own weight only ; and, as the 

 second is stationary, or fixed by the surrounding 

 particles, according to the third law of motion, that 

 action and reaction are equal, it is evident that the 

 action or gravity, in the first, is repelled in an equal 

 degree by the reaction of the second; and, in like 

 manner, the second acts on the third, with its own 

 gravity added to that of the first ; but still the reac- 

 tion increases in an equivalent degree, and so on 

 throughout the whole depth of the fluid. The par- 

 ticles of a fluid, at the same depth, press each other 

 equally in all directions. This appears to rise out 

 of the very nature of fluids ; for, as the particles 

 give way to every impressive force, if the pressure 

 amongst themselves should be unequal, the fluid 

 could never be at rest, which is contrary to experi- 

 ence ; therefore we conclude that the particles press 

 each other equally, which keeps them in their own 

 places. This principle applies to the whole of a 

 fluid as well as a part. For if four or five glass 

 tubes, of different forms, be immersed in water, when 

 the corks in the ends are taken out, the water will 

 flow through the various windings of the different 

 tubes ; and rise in all of them to the same height as 

 it stands in the straight tube ; therefore the drops 

 of fluids must be equally pressed, in all directions, 

 during their ascent through the various angles of 

 the tube ; otherwise the fluid could not rise to the 

 same height in them all. From the mutual pressure 

 and equal action of the particles of fluids, the 

 surface will be perfectly smooth, and parallel to the 

 horizon. If, from any exterior cause, the surface of 

 water has some parts higher than the rest, these 

 will sink down by the natural force of their own 

 gravitation, and diffuse themselves into an even sur- 

 face. See Hydrostatics. 



FLUIDITY; the state of bodies when their parts 

 are very readily movable in all directions with 

 respect to each other. Many useful and curious 

 properties arise out of this modification of matter, 

 which form the basis of the mechanical science called 

 hydrostatics, and are of considerable importance in 

 chemistry. But the attention of the chemist i> 

 chiefly directed to the state of fluidity, as it may 

 affect the component parts of bodies. A solid body 

 may be converted into a fluid by heat. The less the 

 temperature at which this is effected, the more fusible 

 the body is said to be. All fluids, not excepting the 

 fixed metals, appear, from various facts, to be dis- 

 posed to assume the elastic form, and this the more 

 readily the higher the temperature. When a fluid 

 is heated to such a degree that its elasticity is equal 

 to the pressure of the air, its interior parts rise up 

 with ebullition. The capacity of a dense fluid for 

 caloric is greater than that of the same body when 

 solid, but less than when in the elastic state. If this 

 were not the case, the assumption of the fluid arid 

 elastic state would be scarcely at all progressive, 



