122 



HYDROSTATICS. 



sq. cm., then the pressure of 500 Kg. exerted by the small 

 piston will produce a pressure of 500 Kg. x 500 = 250,000 

 Kg. upon the lower surface of the large piston. Hence 

 the following rule : 



v\ xN 

 ^Multiply the pressure exerted by the piston of the 



pump by the ratio between the sectional areas of 

 the two pistons. 



(a.) The accompanying figure shows a device due to Ritchie of 

 Boston. It consists of a base B ; a sliding platform P guided by two 

 vertical pillars ; a bellows-formed rubber bag 

 connecting the base and platform ; and a bag or 

 flask F, fitted with a cap and cork. The flask is 

 connected with the base by flexible tubing. A 

 weight W is placed upon the platform. Fill 

 the globe with water, and elevate it ; the pres- 

 sure of the column will force the water into the 

 bellows, raising the weight ; lower the globe, 

 and the weight will force the water back 

 into it. 



224=. Liquid Pressure Due to 

 Gravity. The pressure exerted by 

 liquids, on account of their weight, may 

 be downward, upward, or lateral. Pres- 

 sure in any other direction may be re- 

 solved into two of these. We shall now 

 briefly consider these three kinds of 

 liquid pressure. 



FIG. 72. 



225. Downward Pressure. Tlie pressure on 

 the bottom of a vessel containing a liquid, is in- 

 dependent of the quantity of the liquid or the 

 shape of the vessel, but depends upon the depth 

 and density of the fluid and the area of the 

 bottom. 



