90 
PROFESSOR W. RAMSAY AND DR. S. YOUNG 
closed limb of A was equal to atmospheric pressure plus or minus the difference of 
levels in the differential gauge, plus or minus the difference of levels in the tube A, 
all reduced to 0°. 
§ 42. Through a second hole in the indiarubber cork D a tube passed to a gauge, F, 
and from that to an exhaust-pump. The mercury in C could thus be caused to boil 
under any desired pressure, heating A to corresponding temperatures. For the 
measurement of these temperatures, Regnault’s data for the vapour-pressures of 
mercury were used. 
Fig. 2. 
§ 43. A preliminary experiment was made in which the tube A contained only 
mercury, which had been repeatedly boiled out in vacuo. The following results were 
obtained:— 
Pressure under which 
mercury boiled. 
Pressure in A. 
a. 
millims. 
millims. 
millims. 
267-6 
266-7 
0-9 
378-3 
377-0 
1-3 
755-0 
751-8 
3-2 
