180 UPWARD PRESSURE IN LIQUIDS. 



column efgh which may be supposed to exist above e 

 Again, the pressure upon e /, in fig. 128, J5, is equal 

 the pressure upon efin fig. 128, -4, if the areas pressi 

 upon and their depths below the top of the liquid ai 

 supposed to be equal, and the upward pressure may 

 calculated on the same principles as the downwai 

 pressure. It follows at once that in a vessel of th< 

 form fig. 128, 5, or one similar to it, the pressur< 

 upon the surface e /, which is equal to the weight oi 

 the liquid column ef g A, may be much greater thai 

 the weight of the liquid actually contained in the vessel 



The upward pressure in a liquid may be shown 

 means of the glass plate represented in fig. 124. A 

 string is attached to the upper end, and passed through 

 the vessels (fig. 120), which is almost completely im- 

 mersed in a rather large jar of water, holding it with 

 the left hand while the string is stretched by the right 

 hand and the plate thus pressed against the rim of the 

 vessel. When the vessel is immersed to the depth 

 shown in fig. 129, the upward pressure of the water 

 sufficient to keep the plate from falling though thi 

 string be let go, the size of the plate and other parts oi 

 the apparatus being supposed to be those specified 

 previously. If the leaden weight has been made too 

 large, and hence the plate too heavy, the weight may be 

 diminished by cutting away a portion of the lead with 

 a knife. 



By means of the Hydrostatic Bellows (fig. 130), a 

 small quantity of water is made to produce considerable 

 upward pressure. It is composed of two flat circular 

 boards united at the sides by flexible leather so as to 

 form a vessel, into the side of which is fixed an upright 



