Pcnone the investigations that the Polar Expedition had placed upon its 
programme, were those for the determination of the variations in the force 
of gravity in different places in the high latitudes which it hoped to reach. 
As, on a journey of this description, there could be no question of anything 
but relative determinations, it was decided, at my suggestion, to employ the 
pendulum apparatus constructed by Colonel von Srerneck, and consisting 
of invariable half-seconds pendulums, of which the period of oscillation is 
determined by the aid of a coincidence apparatus. An apparatus of this 
kind, with two pendulums, was therefore procured for the expedition. Von 
Srerneck was kind enough to determine its constants before it was des- 
patched from Vienna, so that it was possible to refer the observations at each 
place to the actual determination of the acceleration of gravity in Vienna, 
made by Von Oppouzer. As soon as I received the apparatus, I determined 
the period of oscillation of the pendulums in the Observatory in Christiania. 
After the return of the expedition, I subjected the pendulums to fresh exa- 
mination, which showed that they had undergone only an exceedingly slight 
change during the journey. 
In these observations, a half-seconds pendulum clock, Hawex No. 5, 
was employed to work the coincidence apparatus. Before and after each ob- 
servation, which generally lasted */s of an hour, this was compared with a 
mean-time chronometer. In 1892, a chronometer Hohwii 639, belonging to 
the Observatory, and afterwards taken on the Fram expedition, was used; in 
1893 and 1897, a chronometer Michelet 20. The chronometer was compared 
with the Kessels normal sidereal clock of the Observatory, before beginning 
the observations, and after their conclusion, 
