xA_mong 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 STERNECK, 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 

 STERNECK 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 OPPOLZER. 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, HAWELK No. 5, 

 was employed to work the coincidence apparatus. Before and after each ob- 

 servation, which generally lasted 3 /4 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. 



