OF COMPRESSED AIR. 21«3 



stream of air below, and at the last named 

 height, tlie pressure was 4-10tii8 of an inch 

 oj mercury. 



The tube No. 3, shewed its greatest degree of 

 vacuum to be 7-20ths of an hich of mercury, 

 and it was when the valve was up ll-32nds of 

 an inch. As the valve was raised higher, the 

 vacuum became less, until at the height of IJ 

 inches it was nothing. 



In tube No. 4, the mercury began to shew a 

 small degree of vacuum when the valve was 

 raised 3-32nds of an inch ; when it was up i an 

 inch the vacuum was J of an inch, being its 

 greatest degree; from this point the vacuum 

 diminished, and when the valve was l{ inches 

 high, there was very little difference in the levels 

 of the mercury in the two limbs. 



A similar course of experiments was gone 

 through with a valve 8 inches diameter, with 

 some small variations in the results, which were 

 noted in another table; but the only one worth 

 mentioning is, that while the 6-inch valve required 

 a little more than 32 ounces in the scale E, to 

 detach it from its seat, the 8-inch valve required 

 48 ounces. 



From a general view of the results thus 



