MODIFIED BY THE DISCHARGING ORIFICE. 183 



The disk A was three diameters of the orifice in thick- 

 ness^ and was equal to a plain cyhndrical 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 o£ three diameters. 



D had a thickness of twelve diameters of the ori- 

 fice, 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 O 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 

 chamfered to reduce the cylindrical part of the hole as 

 much as possible to a sharp edge. The efi'ect of the 

 chamfering had, however, so small an eff'ect in diminishing 

 the rate of discharge that the determinations might have 

 been taken from the cylindrical 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 1 35 lbs. 

 was discharged into the atmosphere through the orifice in 

 the thin plate O, and through the orifices in A, B, C, J), E 

 successively, and the times were recorded for the reduction 

 of 10 lbs. from each of the atmospheres of pressure, as 

 shown in the following Table : — 



