(25). 
mentioned in D and E. They were determined by suspending all the 
thermometers in a water-bath at a constant temperature, together 
with a standard thermometer of which the scale had been tested at 
the Physikalisch-Technische Reichsanstalt, and of which the zero 
error had been determined every two months in melting ice. 
G. The correction for the compression of the mercury; this is 
A= 1/./? P?, if the coefficient of compressibility is 7. As according 
to AMAGAT /? is only 0.00000392 for mercury if P is expressed in 
atmospheres, this correction need only be considered above 40 atm. 
H. The correction for the lengthening of the measuring rods during 
the suspension. 
The rod Lo was measured in a horizontal position, whereas the 
rods are used, suspended at about 1/3 of their height from the top 
by a Cardanus-collar. Hence the upper part will be compressed and 
the lower part will be lengthened; if / is the distance to the point 
S ; 
of suspension we can easily calculate A = !/s = [2, for the displa- 
cement of the lower end. For brass S — 8.45; E = 1037,000,000 
while / = about 215 em.; so we calculate A = 0.0002 cm. which 
therefore may be entirely neglected. 
§ 3. In order to judge of the influence of the uncertainty in the 
corrections A and B, the open manometer (comp. Communication 
n°. 50 § 2) was divided into two parts (see Plate Comm. n®. 44). 
For this tube A was entirely cut off by closing cock Ky and by 
loosing the steel capillary of tube B, from the T-piece 7), and the 
steel capillary of tube Bs from the T-piece T's, while this opening 
of Ts was closed tightly by a nut with leather packing. If all the 
other cocks are open and pressure is very slowly admitted by means 
of cock X, we shall see the mercury rise in the capillary both in 
tube 5; and Bs. If in B, the mercury has reached the mark X, the 
cock Ks is closed, after which the mercury is forced up in Bg, ete. 
At the same time attention must be paid to the mercury in Bs and 
the cock Ky is closed when the mercury in Bs has reached the 
required height, which now however will be higher than the mark 
Xs of the figure and which must be determined experimentally 
beforehand. In this way we can continue until the mercury has 
reached the lower end of the upper reservoir in tube B, and there- 
fore also in By,; then the cock Ag is closed while the cock X is 
left open until the mercury in tube Zj, has reached the upper 
