OF COMPRESSED AIR. 211 



procured, and proper quantities of mercury being 

 put into them, they were inserted in holes made 

 tlirough the valve at certain distances from each 

 other, as shown in Figure the first, 1, 2, 3, 4. 

 The inserted limbs of these tubes being thus left 

 exposed to the action of the stream of air, the 

 compressed air was again admitted into the 

 pipe A, and the valve rose as before, l-d2nd 

 of an inch. 



The tube No. 1, in that part of the valve D, 

 wliich was over the aperture B, had the mercury 

 in it 14 inches higher in the outer than in the 

 inner limb, and consequently shewed a pressure 

 from the compressed air below it, above atmos- 

 pheric pressure, equal to \\ inches of mercury. 

 The tube No. 2, which was near to the aperture 

 B, but over the inner edge of the seat C, shewed 

 a rise of the mercury of 3-lOths of an inch in 

 the inner limb of the tube, and consequently a 

 pressure from the air below it less than atmos- 

 pheric pressure by 3-lOths of an inch, — or a 

 partial vacuum of 3-lOths of an inch of mercury. 

 The tube No. 3, at the same time shewed a 

 similar vacuum of 1-8 of an inch of mercury. 

 The mercury in the tube No. 4, was undisturbed. 



The valve with the four tubes in it was now 

 raised above its seat from l-32nd of an inch until it 

 2d2 



