178 PROF. OSBORNE REYNOLDS ON 



and if the temperature is 57° ¥., as in Mr. Wilde^s expe- 

 rimentSj 



U„=I022. . . (14) 



Reducing this in the ratio of the density at the neck to 

 the density in the discharging vessel,, 

 I 



^"-^5^n (15) 



^,=•6345 j 



We have the reduced velocity 



U„^ =650 (feet per sec.) (16) 



Pi 



Therefore the discharge will be given in cubic inches 

 per second, KO being the effective area of the orifice, by 



p.Q=i2U„p„K0 I , ^^ 



= 12 X650KOJ * , * 



Or, since the actual area in square inches 



= '000314 sq. inches, 



Q = 2*44K (cubic inches per sec). . (18) 



10. In order to compare the experimental discharges 

 with those calculated, it is necessary to know, besides the 

 size of an orifice and the pressure and temperature of the 

 discharging vessel, the coefficient of contraction or the 

 effective area of the orifice. To obtain this from the 

 equations requires that the terms depending on viscosity 

 should be introduced, which renders the integration so far 

 impossible. The only plan is to obtain this coefficient by 

 comparing the theoretical results with the experimental. 

 Such comparisons have been made by Prof. Weisbach for 

 air ; and in the case of short cylindrical orifices such as 

 that used by Mr. Wilde (a cylindrical hole through a 

 plate having a radius equal to the thickness of the plate). 



