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was 26 feconds;, when the experiment was repeated precifely in 

 the fame manner, but in the open air, the time of the efflux was 

 only 19 feconds. Now as the gage flood at 28,5, the defed D 

 was 30 — 28,5 = 1,5, and the preffure on the plate of mercury was 

 = 6 ^ i^ = 75^ ; in the open air the prefTure was = 6 + 7.8 = 

 r3,8j therefore the ratio of the velocity of the efflux in both 

 cafes, which is the fame with tlie reciprocal ratio of the times, 

 was •^']\ to v'13,8, or as 2,73 to 3,7 ; but 2,73 is to 3,7 as 19 to 

 26 very nearly. No difference was obferved in the times of the 

 efflux, when in the open air and exhaufted receiver, unlefs the 

 gage flood higher than 225- inches ; that is, unlefs the height of 

 the mercury in the gage was greater than the difference between 

 the length of the pipe and the flandard altitude. In another ex- 

 periment, when the gage flood at 27,9, the height of the barometer 

 was 29,9 ; the defed therefore was := 2, and the prefTure = 8. 



But *^8"= 2,828, and */i3,8 = 3,7 but 2,828 : 3,7 : : 19 : 24, and 

 by experiment the time of the efflux appeared to be 23 feconds. 

 When the efflux is made in vacuo, it is obvious to obferve, that 

 the pipe is not filled during the efflux, as it is while the difcharge 

 is made in the open air. 



Since the column of water in the pipe mnrs adds fo the 

 preflure which the plate w ?/ fuftains, by diminifhing the upward 

 preffure of the air through the pipe, it appears that it produces 

 this increafe of prefTure in the plate mn alone, without producing 



any 



