536 



Mr. H. Wilde on the Velocity 



Table I. — Discharge into a Vacuum 0*6 inch Mercury. 

 Barometer 29*42. Thermometer 54° F. 



Absolute pres- 



Time of 



Velocity, in 

 feet per second. 



Velocity 



sure, in pounds 

 per square inch. 



discharge, 

 in seconds. 



coefficient 

 •62. 



135 



7-5 



750 



1210 



130 



7-75 



753 



1214 



125 



80 



759 



1225 



120 



8-5 



743 



1198 



115 



90 



• 734 



1184 



110 



9-5 



726 



1171 



105 



10-0 



724 



1168 



100 



10-5 



722 



1165 



95 



110 



725 



1169 



90 



12-0 



703 



1134 



85 



130 



688 



1109 



80 



140 



678 



1094 



75 



150 



675 



1089 



70 



16-5 



657 



1060 



65 



180 



650 



1048 



60 



20-0 



632 



1020 



55 



22-0 



628 



1011 



50 



24-5 



620 



1000 



45 



270 



624 



1007 



40 



31-0 



613 



985 



35 



36'0 



602 



971 



30 



430 



589 



950 



25 



53-0 



573 



924 



20 



690 



550 



887 



15 



97-0 



522 



842 



10 



170-0 



446 



720 



From this table it will be seen that the time of discharge 

 of 5 lb. from 135 lb. absolute pressure is 7*5 seconds. Now, 

 as 5 lb. pressure is the ^j part of the total pressure, we have 

 573 



27 



= 21*22 cubic inches of air from 135 lb. pressure dis- 

 charged into the vacuum chamber in 7*5 seconds : or, in 

 another form, since 5 lb. and 191 cubic inches of air at atmo- 

 spheric pressure are equivalents, so 191 cubic inches condensed 



191 

 to 9 atmospheres -^—=21*22 cubic inches of discharge, as in 



the above calculation. Again, we have for a cubic inch ex- 

 tended into a cylinder O02 of an inch in diameter (the size of 

 the discharging orifice), 265*25 feet x 21*22 = 5628 feet. 

 5628 feet 



Hence V = 



7*5 seconds 



= 750 feet per second for the discharge 



of air from 135 lb. to 130 lb. into a vacuum through a hole in 



750 

 a thin plate. Or V= -^ =1210 feet per second when the 



orifice is formed to the contracted vein. By the like method 



