Chap. 3.] through Conduit Pipes. 465 



B C ; the water having arrived at the bending C, will 

 flow down the lower part of this bending, and will pro- 

 ceed to fill the bending D, leaving behind it the co- 

 lumn of air C D, which cannot efcape. The water, 

 continuing to run, will rife from D to E, and having 

 arrived there, it will ftill flow down the lower part of 

 this declivity to fill the bent F, leaving behind it a fe- 

 cond column of air E F, which will remain confined 

 there, notwithstanding the preflure of the column A B ; 

 for the column of air C D cannot counterbalance the 

 preflure of the column of water D E, any more than 

 the column of air E F is capable of counterbalancing 

 the column of water F I ; fo that though the water in 

 the pipe A B is confiderably above the level G, the 

 water can only rife towards I, and there ceafes to flow* 

 The only remedy is, to let out the two columns of air 

 C D and E F, by placing at the elbow of the bendings 

 two fmall pipes C and E, through which the air may 

 efcape, and when the courfe of the water is well ar- 

 ranged the apertures may be clofed with bungs. 



VI. Of the ofcillatory motion of water in a fiphon. 



It is well known that the duration of the ofcilla- 

 tions of two pendulums of unequal lengths are to 

 each other as the fquare roots of thofe lengths. The 

 ofcillatory motion of water in a fiphon is of the fame 

 nature. 



Suppofe a fiphon (Fig. 2.) compofed of three 

 branches, two vertical / n, m 0, and one horizontal o ; 

 fuppofe that the interior diameter of the fiphon is equal 

 through its whole extent; that in this fiphon, the fluid, 

 in a ftate of reft, occupies the fpace anod-> then the 

 two furfaces a b, c d, are upon a level. Suppofe then, 

 that, by fome caufe, the liquid is forced to defcend tog h* 

 in the branch m t, and confequenUy to elevate itfelf to 



VOL, II. H h /, 



