56 O. E. SCHIOTZ. [NORW. POL. EXP. 
At Khabarova, where the observations as a whole were not so successful, 
the period for pendulum 34, as has been already mentioned, was found too 
small, on account of the rapid rise in the temperature during the experiments. 
Even with the highest value, which is the only one retained above, the dif- 
ference in question is only 2356 10~‘. For this reason, I have thought it 
best to give the period of oscillation for pendulum 34, half the weight of that 
for pendulum 33. If we suppose, moreover, that the difference between the 
periods of oscillation is 2447 < 10‘, we find the mean period of oscillation 
of the two pendulums to be 0°5058721, the value given in the table. 
What distinguishes the above observations of the Fram expedition from 
others that have hitherto been made, is that they have been made upon the 
open sea, over depths of water of more than 2000 metres. They were rendered 
possible by the fact that the vessel was frozen into the sea-ice, and drifted 
with it. The great pressure, however, to which the ship was exposed, even 
in the middle of winter, shows that this mass of ice cannot be regarded 
at all times as one coherent layer, drifting along with one motion for the 
whole. The various parts of the ice-covering may be moving at variance 
with one another, and this movement may be carried so far as to cause the 
ice-covering to burst at such places where the compression or distention be- 
comes too great. If this be the case, it is to be feared that even if the ice 
is apparently motionless, there may be imperceptible movements and trem- 
blings in the covering that may affect the oscillations of the pendulum. 
The influence that the motion of the ice may have upon the pendulum’s 
period of oscillation ought therefore to be more carefully investigated. It is 
easy to show that a simple motion of translation, even if not uniform, but 
uniformly accelerated or retarded, will produce no change in the period of 
oscillation; the motion need not, I presume, be imagined to be more com- 
plicated than this in the comparatively short time that each observation lasts, if 
it is possible at all to consider the motion of the ice to be regular. The case 
would be different with the irregular movements and tremors of the ice. As 
I have attempted to demonstrate in a previous work!, these tremors of the 
1 QO. E. Scurorz, Resultate der im Sommer 1893 in dem nérdlichsten Theile Norwegens 
ausgefiihrten Pendelbeobachtungen nebst einer Untersuchung iiber den Hinfluss von 
Bodenerschiitterungen auf die Schwingungszeit (Kristiania, J. Dybwad 1894.) p. 15 
et seq. 
