ILLUSTRATED BY EXPERIMENTS. 



157 



thing, one Ib. of water in the tube, will suspend the top of the vessel, 

 together with the load upon it, supposing them to weigh conjointly 

 900 Ibs. 



EXPERIMENT 2. Let mno represent a vertical section of a spherical 

 vessel filled with water, or some other incompressible and non-elastic 

 fluid, and let AB be a common 

 tumbler glass, held vertically with 

 its mouth exactly in contact with 

 the fluid's surface ; then it is mani- 

 fest, that in this state the glass is 

 completely rilled with air of the 

 natural density ; that is, with air of 

 the same density as atmospheric air 

 on the surface of the earth. 



If the tumbler be still held in a 

 vertical position, but a little depressed below the surface of the fluid, 

 as represented by c D, then it is obvious, that a small quantity of the 

 fluid has entered, and the rest of the glass is filled with air in a state 

 of slight condensation, corresponding to the pressure of the super- 

 incumbent column of water represented by T>d. And moreover, if the 

 glass be still farther depressed, the fluid will ascend higher and higher, 

 and the air will be compressed into a less and less space. 



Again, if the glass be inclined in any degree from the vertical 

 position, as represented by EF and GH, taking care to have its mouth 

 wholly immersed in the water, then it is evident, that the greater the 

 degree of inclination, the greater is the quantity of fluid which enters, 

 and the greater also is the condensation of the included air; but when 

 the quantity of fluid which enters the glass is the same, both in the 

 vertical and the inclined position, the density of the air is also the 

 same, being compressed by the same force ; consequently, the water 

 or fluid in which the glass is placed, exerts the same pressure in 

 whatever direction it is propagated. One sees this experiment verified 

 daily by empty casks having only one end, thrown into water. 



EXPERIMENTS. If the several tubes A, B, c, D A;B 

 and E, bent at various angles, be .inserted in an 

 empty vessel, or if they be held in the hand, and 

 mercury be introduced at their lower extremities, 

 in such a manner, as to come close to the ori- 

 fices ; then let water be poured into the vessel, 

 and it will be seen, that during the time of its 

 filling, the mercury is pressed gradually from the 



