modified by the Form of the Discharging Orifice. 495 



The disk A was three diameters of the orifice in thickness, and 

 was equal to a plain cylindrical tube three diameters in length. 



Disk B was the same thickness as A, but the hole was coned 

 out on one side to a depth of one diameter and a half. 



C was six diameters in thickness, and was coned out on 

 one side to a depth of three diameters. 



D had a thickness of twelve diameters of the orifice, and 

 was coned out on one side to a depth of six diameters. 



E was eighteen diameters of the hole in thickness, and was 

 coned out on both sides to a depth of six diameters, which left 

 a plain tube in the centre of the disk six diameters in length. 



The wide sides of the coned orifices were equal to two 

 diameters, and their outer edges were rounded off to a 

 conoidal form. 



The thin iron disk was *007 of an inch in thickness, or 

 nearly one third the diameter of the orifice, which was two 

 hundredths of an inch. One side of the orifice was cham- 

 fered to reduce the cylindrical part of the hole as much as 

 possible to a sharp edge. The chamfering had, however, so 

 small an effect in diminishing the rate of discharge, that 

 the determinations might have been taken from the cylin- 

 drical orifice without interfering with the general accuracy 

 of the results. 



The mode of experimenting was similar to that already 

 described. Air of an initial absolute pressure of 135 lb. was 

 discharged into the atmosphere through the orifice in the 

 thin plate 0, and through the orifices in A, B, C, D, E 

 successively, and the times were recorded for the reduction of 

 10 lb. from each of the atmospheres of pressure, as shown in 

 the following table : — 





Table I. — Discharge 



into the Atmosphere. 





Lb. per 



square inch 



absolute 



pressure. 



.as 



OS 



£ 8 



.a? 



c3 O 



Conoidal 

 orifice 

 inside. 



Conoidal 

 orifice 

 inside. 



Conoidal 

 orifice 

 inside. 



Double 



conoidal 



orifice. 



* s 



*H o 

 Q o 









A 



B 



C 



D 



E 







135 



sec. 

 15-5 



sec. 

 14-5 



sec. 

 14-5 



sec. 

 14-5 



sec. 

 15-0 



sec. 

 15-5 



•935 



120 



17-5 



16-5 



16-5 



16-5 



17-0 



17-5 



•943 



105 



20-5 



190 



190 



190 



20-0 



20-5 



•927 



90 



25-0 



23-5 



23-5 



235 



24-5 



25-0 



•940 



75 



31-5 



29-5 



29-5 



29-5 



30-5 



31-5 



•936 



60 



42-0 



395 



39-5 



39-5 



41-0 



42-0 



•940 



45 



58-0 



54-5 



54-5 



54-5 



56-5 



58-0 



•940 



—— — — 



Mean coefficient for orifice in thin plate, *937. 



