186 MR. H. WILDE ON THE EFFLUX OF AIR AS 



On comparing the times of discharge through the several 

 orifices among themselves,, and with those in Table I., a 

 marked difference is observable in them. Thus the ratio 

 of discharge through the tube orifice A and the orifice in 

 a thin plate is greater than that for the same orifices in 

 Table I., the coefficients for the highest and lowest pres- 

 sures in this Table being "935 and '940 respectively; 

 whereas the coefficients for the same orifices in Table II. 

 are "829 and 765 respectively. Again^ while there is 

 little diff'erence in the times of discharge from" the tubular 

 orifices among themselves^ a remarkable change occurs 

 duriag the fall of pressure from 15 lbs. to i lb., when the 

 discharge is made through C and D with the conoidal 

 orifices outside the vessel. 



The discharge through D from 15 lbs. to 13 lbs. is the 

 same whether the conoidal orifice is inside or outside ; 

 but in the latter position, as the pressure diminishes, the 

 rate of discharge increases, till at the lowest pressure this 

 increase amounts to 8*5 seconds, and exceeds the maximum 

 discharge from the tube orifice A. A similar change is 

 also noticeable in the rate of discharge through reversing 

 the orifice C ; but as the change does not come on before 

 the pressure is below 7 lbs., it is less marked than when 

 the discharge is made through D. 



Suspecting that the phenomenal change in the rate of 

 discharge for the same orifice was due to the varying 

 resistances of the discharging and receiving atmospheres 

 of pressure described in my former paper, the discharges 

 from the orifices O, A, and D were made into a vacuum 

 of I '5 inch of mercury instead of into the atmosphere, 

 and the times of discharge were recorded for each reduc- 

 tion of I lb. of pressure. 



The results are shown in the Table : — 



