( 26 ) 
part of the reservoir; then also the cock X is closed !). In this way 
it was possible to raise the pressure in the second system of tubes 
more than !/, atm. higher than in the first system. At the reopening 
of the cock Kg the communication between the two systems was 
reestablished and thus while the pressure rose for the first system it 
fell for the second. The influence both of the friction and of the 
depressions was opposite for the two systems, for in the first 
system the menisci were rounded at the upper end and flat at the 
lower end, whereas in the second they were rounded at the lower 
and flat at the higher end. As during the reading which lasted each 
time 30 minutes we could expect a variation of the menisci the 
observations have each time been made symmetrically, and so first 
in system I at the higher end from the left to the right, then in 
system IT at the higher end from the left to the right, then in 
system II at the lower end from the right to the left and lastly in 
system I at the lower end from the right to the left. 
§ 4. Results. In order to give a survey of the value of the cor- 
rections to be applied and the calculation of the pressure this has 
been carried out for one measurement. For the further determinations 
which will be communicated in the table of comparisons (p. 28) all 
the pressures are similarly calculated’). 
In order to obtain the uncorrected height at the mean time viz. 
at 4.36 we need only add to the sum of the lengths of the measuring 
rods (entered in the table for both system as =/L and 2//L), the 
sum of the upper readings (for both systems 2/8 and =,//B) 
taking into account that the measuring rod L serves as well for the 
manometer tube B, as for B, ete. and to subtract from this sum the 
sum of the lower readings (for both systems ZB and Z,/B). In 
determining the mean temperature given as T\/ and TZ etc. we 
must pay attention to the positions of the thermometers; they were 
arranged in the following way: tb, fo and f, were suspended at the 
upper end, in the middle and at the lower end of tube B; f4 and 
t; were suspended at 1/, and 3/, of the tube B, and 4, t; and ¢s again 
1) In order to exclude unnecessary possibilities of leakage the differential mano- 
meter tube C was always loosened from the T-piece Zi, and the crosspiece N, which 
were both again closed. 
2) In this equation the height of the barometer can be left out of consideration, 
because it equally influences both systems. 
nn © U 
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