SCIENCE AS MEASUREMENT 97 



by a well-lighted staircase, the tube being suspended 

 by strings.) The glass was heated more than a foot 

 from the lower end, and bent so that the shorter leg 

 of twelve inches was parallel with the longer. The 

 former was hermetically sealed at the top and marked 

 off in forty-eight quarter-inch spaces. Into the open- 

 ing of the longer leg, also graduated, mercury was 

 poured. At first only enough was introduced to fill 

 the arch, or bent part of the tube below the gradu- 

 ated legs. The tube was then inclined so that the air 

 might pass from one leg to the other, and equality 

 of pressure at the start be assured. Then more mer- 

 cury was introduced and every time that the air in the 

 shorter leg was compressed a half or a quarter of an 

 inch, a record was made of the height of the mercury 

 in the long leg of the tube. Boyle reasoned that the 

 compressed air was sustaining the pressure of the 

 column of mercury in the long leg plus the pressure 

 of the atmosphere at the tube's opening, equivalent 

 to 29 ^g- inches of mercury. Some of the results were 

 as follows : When the air in the short tube was com- 

 pressed from 12 to 3 inches, it was under a pres- 

 sure of H7y 9 inches of mercury; when compressed 

 to 4 it was under pressure of 871J inches of mer- 

 cury ; when compressed to 6, 58 1| ; to 9, 39|. Of 

 course, when at the beginning of the experiment 

 there were 12 inches of air in the short tube, it was 

 under the pressure of the atmosphere, equal to that 

 of 29^- inches of mercury. Boyle with characteristic 

 caution was not inclined to draw too general a con- 

 clusion from his experiment. However, it was evi- 

 dent, making allowance for some slight irregularity 

 in the experimental results, that air reduced under 



