APPLICATIONS OF MAKIOTTE'S LAW. 261 



surface of the liquid were at d, and it remains constant 

 as long as d and b maintain their relative distance. 

 Hence while the rate at which a liquid flows from a 

 common vessel is continually decreasing, it remains 

 uniform in a Mariotte's bottle until the surface of the 

 liquid sinks below d\ and by moving the tube up or 

 down the rate may be regulated at will. In the figure 

 181 J., be represents the form of the jet which issues 

 from &, if the end of the tube c d is at d-, if the end 

 were at d^ the jet would have the form b e^ and if the 

 tube were pushed down to d. 2 , the velocity of efflux 

 would be considerably diminished, and the issuing jet 

 would have the form b e. 2 . Finally when d is at the 

 same height as , the pressure is equal at both points, 

 and the flow ceases, 



A common bottle may be converted into a Mariotte's bottle by 

 boring, a lateral orifice in the manner explained on p. 41, or, as 

 shown in fig. 181 JB, a siphon may be passed through the neck of the 

 bottle and used as a discharge-tube. 



If air and water are in contact in a confined space, 

 is is the case in Mariotte's bottle, and the surface of 

 ;he liquid is higher than the point where it is in contact 

 vith the external air, the efflux of the liquid will 

 violently afford more room for the air, the latter will 

 'xpand, and the increase of its volume will diminish 

 ! he pressure. It follows that the excess of the 

 tniospheric pressure over that of the confined air 

 :onstitutes a force which may be employed for driving 

 vjiter or air into the enclosed space. A capacious 

 ottle, fig. 182, is tightly closed by a cork through 

 v r luch pass two tubes ; one is somewhat long and 

 t might, the other is bent twice at right angles and 



