58 0. E. SCHIOTZ. [NORW. POL. EXP. 
June is as much as 145 units in the seventh decimal-place less than. that 
found on the 10th, although the two points of observation lay no more than 
about 5 km. apart, above a depth of over 3000 metres. If we especially exa- 
mine the period for pendulum 34, with which experiments on the 8th, 
10th and 11th June were made, we find that the period decreases regularly 
from the 8th — when, as we shall subsequently see, it was about normal — to 
the 11th. We must suppose that after the violent wind of the 9th June, 
internal tremblings have commenced in the ice-masses, and have increased in 
strength on the 10th and 11th, as the force of the wind diminished, and the 
rate of the drift became slower. I think we may conclude that this has really 
been the case, from the fact that Lieut. Scott-Hansen, on the 11th, expressly 
mentions that he heard rumblings in the ice during the first comparison of 
clocks, previous to the commencement of the pendulum observations. These 
observations are thus easily explained by the influence — already pointed 
out by me — of imperceptible tremblings upon a pendulum’s period of 
oscillation. 
As the observations show, the pendulums have only altered in a very 
slight degree during the expedition. The mean period of oscillation before 
the departure of the expedition was 0:5060400 in the Observatory, and after 
its return, 0°5060389 in the new pendulum-house in the Observatory Garden. 
The difference only amounts to 11 units in the last decimal-place, and 4 or 
5 of these may be attributed to the difference in elevation — 5°6 m. — between 
the two points of observation’, thus leaving a difference of only 7 units 
due to an alteration of the pendulums during the expedition. This alteration 
is so small that the pendulums may safely be considered as unchanged during 
the expedition, with a mean period of oscillation in the Observatory equal to 
0:5060397, corresponding to the mean of the period of oscillation in the same 
place before and after the journey. 
If we start with the value found by Von Opprouzer for the acceleration 
of gravity in Vienna (Tiirkenschanze), viz. 
g = 980866 m., 
1 When the new pendulum-house was taken into use, an attempt was made to deter- 
mine directly the difference between the periods at the two places. No certain diffe- 
rence was obtained. 
