153 



MR. H. WILDE ON THE VELOCITY 



large cylinder B was first used as a vacuum-chamber to 

 receive the discharge from the small cylinder. The 

 chamber was fitted with an exhausting pump and suitable 

 vacuum-gauges^ and the pressure within the chamber was 

 reduced to six tenths of an inch of mercury ; and that 

 degree of vacuum was maintained during the experiments. 

 The following Table shows the velocity of air flowing 

 into a vacuum, as deduced from the time and difii'erence of 

 pressure for every 5 lb. from 135 lb. to 5 lb. absolute 

 pressure. The velocities of the first column are deduced 

 from actual experiments, and in the next column the 

 velocities are calculated from the difference of the area of 



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

 Barometer 29*42. Thermometer 54° F. 



Absolute pres- 



Time of 



Velocity, in 



Velocity 



sure, in pounds 



discharge, in 



feet per 



coefRcient 



per square inch. 



seconds. 



second. 



■62. 



135 



7-5 



750 



1210 



130 



775 



753 



1214 



125 



8-0 



759 



1225 



120 



8-5 



743 



1198 



"5 



9-0 



734 



1184 



no 



9'5 



726 



1171 



105 



lO'O 



724 



1168 



100 



10-5 



722 



1165 



95 



no 



725 



1169 



90 



I2-0 



703 



1134 



85 



13-0 



688 



1 1 09 



80 



i4'o 



678 



1094 



75 



15-0 



675 



1089 



70 



i6-5 



657 



1060 



65 



i8-o 



650 



1048 



60 



20'0 



632 



1020 



55 



22'0 



628 



lOII 



50 



24-5 



620 



1000 



45 



27-0 



624 



1007 



40 



31-0 



613 



985 



35 



36-0 



602 



971 



30 



43-0 



589 



950 



25 



53'o 



573 



924 



20 



69-0 



550 



887 



15 



97-0 



522 



842 



10 



1700 



446 



720 



