HYDliAULICS. 101 



measured by rules, and the just estimate of their influence 

 must depend on experience. 



1. Water will flow more rapidly from an aperture in a 

 vessel if a funnel-shaped tun or a rapidly widening trough 

 be attached to it on the outside. This prevents, so to 

 speak, the intercrossing of the currents as they flow over 

 the sides of the aperture ; instead of obstructing itself, by 

 reason of its tendency to cross the centre of the opening, 

 the water follows the sides of the funnel or trough, and 

 allows the full area of the opening to discharge freely. 



2. The ease with which a given quantity of water can 

 be made to pa'ss through a pipe depends (other things 

 being equal) upon the proportion between the area of the 

 opening and st circumference the latter being a source 

 of friction. (See Nos. 14 and 11 above.) 



3. The ease of the flow depends on the perfect uni- 

 formity of the channel. A lump or any other inequal- 

 ity in the side of a pipe will disturb the current and cause 

 the water to obstruct itself. Perfect form is more import- 

 ant than a smooth surface. 



4. The same principle operates in the case of deflections 

 from a straight line. If the water is turned out of its 

 course the evenness of the flow is disturbed, and it becomes 

 more difficult (see No. 18 above). The influence of a 

 "regular curve" is in proportion to its radius; more 

 water will flow through a pipe which turns in a large circle 

 than in one which turns more abruptly. 



