281 Prof. W. C. Unwin on the Discharge of Water 



190° 



130° 



60° 



Coefficients of Discharge. 



Fall of level Fall of level 



from A to B. from A to C. 

 ■1)813 J -9859 



•9896 \ -9915 



•9730 -9750 



'9338 f -9435 



9414 1 -9486 



( -98: 

 \-98! 



{ 



Mean Values of c. 



190° 0-9871 



130° 0-9740 



60° 0-9418 



The experiments on a conoidal orifice having shown a small 

 but definite influence of temperature on the discharge, it 

 seemed desirable to try whether a similar effect would be pro- 

 duced in the case of a thin- edged orifice. With the conoidal 

 orifice there is no contraction of the jet, and the discharge is 

 less than the so-called theoretical discharge by an amount de- 

 pending only on the friction of the orifice. In the case of 

 a thin-edged orifice, the jet contracts to an area of about f 

 that of the orifice ; and the discharge is diminished not only 

 by the friction, but also to a much greater extent by the con- 

 traction. The thin-edged orifice was 1 centimetre diameter ; 

 and the heads were nearly the same as before. 



Experiments on Thin-edqecl Orifice, 1 centim. in diameter, 

 June 12, 1878. 



Temperature, 

 Fahrenheit. 



205 . 



205 . 



140 . 



65 . 



61 . 



61 . 



62 

 140 

 205 



Time of discharge 



of water between 



A and B in fifths 



of a second. 



503 



500 



507 



500 



495 



495 



Mean Values. 



. . 496-6 

 . . 507-0 

 . . 501-5 



Time of discharge 



of water between 



A and C in fifths 



of a second. 



748 



747 



744 



746 



740 



740 



742 

 744 

 747-5 



The times here recorded show that, in the case of a thin- 

 edged orifice, the temperature has an extremely small influence 



