154 



MR. H. WILDE ON THE VELOCITY 



considering tlie velocity of air discharged into tlie atmos- 

 phere. Meanvrhile I may remark that the velocities 

 increase with the pressures by small asymptotic quantities^ 

 so that the theoretic velocity of 1332 feet per second 

 would be obtained at a pressure of 40 atmospheres if the 

 law of Boyle and Mariotte held good for so high a density. 



While the rate of each discharge may be considered 

 approximately uniform for the higher pressures, the initial 

 and terminal velocities of each discharge of 5 lb. for the 

 lower pressures would be much different. This is specially 

 noticeable for the velocity (842 feet per second) assigned 

 to atmospheric pressure of 15 lb. ; and as it was a matter 

 of much interest that this important constant of nature 

 should be determined with all the accuracy attainable, 

 experiments were made to ascertain the velocity of dis- 

 charge for every pound of pressure from 15 lb. to 2 lb. 

 In these experiments the readings were taken from the 

 mercurial gauge, and the vacuum in the chamber was 

 reduced to 0*4 of an inch of mercury. 



The results obtained are shown in the Table. 



Table II. — Discharge into a Vacuum 0*4 inch Mercury. 

 Barometer 29'96. Thermometer 60° F. 



Absolute pres- 



Time of 



Velocity, in 



Veloeity- 



sure, in pounds 



flischarge, in 



feet per 



coefBcient 



per square inch. 



seconds. 



second. 



•62. 



15 



i6-o 



633 



I02I 



14 



17-5 



621 



lOOT 



13 



19-0 



614 



990 



12 



21*0 



606 



977 



II 



23-0 



600 



968 



10 



25-5 



596 



961 



9 



28-5 



593 



956 



8 



3i'5 



584 



942 



7 



37-5 



577 



931 



6 



45-0 



563 



908 



5 



55-0 



559 



901 



4 



yo'o 



542 



874 



3 



I02-0 



497 



802 



2 



i8o-o 



421 



679 



