(114 ) 
For the way in which we derive from this the pressure at 4 p.m 
and 4.19 p.m. I refer back to the Proceedings of May 25th ’01 
(Comm. N°. 70 § 4); only the barometer height must be added to 
this, and it must be taken into account that the aneroid was on 
the same height as the zero of the measuring rod suspended between 
the limbs of tube A. The correction for the compression of the 
mercury was applied to pressures above 32 atm. (Comp. Proceedings 
of May 25% ‘Ol, Comm. N® 70° § 2: G.). 
To obtain the pressure at 4.7 p.m. I assumed that the pressure 
varied proportionally with the time. 
The pressure now measured is that of the lower reservoir of the 
last manometer tube in use; the mercury height in this agreed 
always within a few centimeters with the height in the level-glass 
of the piezometers, The correction for the hydrostatical pressure 
in the gas, which transfers the pressure, may then be neglected. 
In measuring the excess of pressure, caused by the difference in 
mercury level in the piezometer tube and in the level-glass, we 
must bear in mind that the temperatures of those columns are 
generally different. However the error is sure to remain within the 
limits of observation if we assume that the mercury in the steel 
flanged tube 10 c.m. below the water bath has reached the temper- 
August 25th TABLE I. 
Corrected Barom, Reading Corr. uae Gann fae | Corr. 
Time. | mere. height | at level of for height 
open manom.| mercury. ee | depress. mute. peat level gl. 
2.40 2639. 47 | 
2.48 | 75.91 31.418 0.110 | 19°.3 | — 0,098 | 32.23 
3.00°| 2638.36 
3.09 75.92 31.448 | 0.110 | 19°.3 | — 0.098 | 32.24 
3.205} 2636.63 
3.28 75.93 31.427 0.115 | 19°.2 | — 0.098 | 32.19 
3.40 2635.09 
3.48 75.94 31.429 0.144 | 19°.1 | — 0.097 | 32.21 
4.00 2633. 59 
4.07 75.95 31.426 0.107 | 19°.1 | — 0.097 | 32.22 
4.19 2631.83 
4.265 75.96 31.423 0.144 | 19°. | — 0.C97 | 32.21 
4.385| 2630.50 | 
