540 Mr. H. Wilde on the Velocity 



Table IV. — Discharge into the Atmosphere. 

 Barometer 29*64. Thermometer 58° F. 



Effective pres- 



Time of dis- 



Apparent 



Velocity- 



sure, in pounds 



charge, in 



velocity, per 



coefficient 



per square inch. 



seconds. 



second. 



•62. 



120 



75 



843 



1360 



115 



7-75 



852 



1374 



110 



8'0 



862 



1390 



105 



8-5 



852 



1374 



100 



9-0 



843 



1360 



95 



9-5 



842 



1360 



90 



10-0 



843 



1360 



85 



10-5 



851 



1372 



80 



11-0 



863 



1392 



75 



12-0 



844 



1362 



70 



130 



836 



1348 



65 



140 



833 



1344 



60 



150 



843 



1360 



55 



165 



837 



1350 



50 



180 



843 



1360 



45 



20-0 



843 



1360 



40 



22-0 



863 



1392 



35 



24-5 



886 



1429 



30 



27-0 



935 



1509 



25 



31-0 



980 



1581 



20 



30-0 



1053 



1699 



15 



43-0 



1178 



1900 



10 



58-0 



1311 



2114 



In this table it will be observed that the times of each 

 discharge from 120 lb. to 15 lb. effective pressure into the 

 atmosphere are identical with the times of discharge from 

 135 lb. to 30 lb. absolute pressure into a vacuum. Hence we 

 are able to formulate and prove the general proposition that 

 the atmosphere acts as a vacuum, and offers no resistance to 

 the discharge of air of all pressures above tivo absolute 

 atmospheres. 



Although the times of discharge for each reduction of 5 lb. 

 of pressure, as we have seen, are the same as those for pres- 

 sures one atmosphere higher, when the discharge was made 

 into a vacuum, yet it seemed to me that a table showing the 

 apparent velocities due to the effective pressure would be 

 useful as exhibiting some further points of interest, and re- 

 vealing the fallacy involved in estimating the velocities from 

 the effective pressures. On comparing the velocities of each 

 discharge from 120 lb. to 40 lb., it will be seen that the theo- 

 retic velocity of 1332 feet per second is as"„n early attained as 

 the units of pressure and time adopted in these experiments 



