TENSION OF OASES. 



165 



L 



FIG. ico. 



same horizontal line. By holding the tuhe nearly level, 

 bubbles of air may be passed into the short arm or from it 

 until the desired result is secured. The air in the short 

 arm will then be under an ordinary atmospheric pressure. 

 As more mercury is poured into the long arm the confined 

 air will be compressed. 



(a.) When the vertical distance between the levels of the mercury 

 in the two arms is one-third the height of the barometric column 

 at the time and place of the experiment, the pressure upon the 

 confined aii will be f atmospheres ; the tension of the confined air 



