PENDULUM OBSERVATIONS 
457 
referred to similar observations at the standard station 
in Potsdam. 
The pendulums used were of Col. von Stcrneck's 
pattern and are gilt, three in number, swinging from agate 
planes in two directions at right angles to one another. 
The pendulums are swung at atmospheric temperature 
and pressure, and corrections are applied to reduce to 
normal. 
The time of swing is measured by the method of 
coincidences, with reference to a special clock making 
an electric contact each second. This clock is used as 
the standard and rated (if possible) to iV^h second in the 
day, by observation of stars at meridian transit. 
With care the value of ' g ' should be accurate, after 
all corrections are applied, to one part in a million, but 
under the particularly unfavourable conditions in the 
Antarctic it is doubtful if a much higher accuracy than 
I in 250,000 is obtainable. 
The difficulties experienced with the instrument in 
the Antarctic, though apparently trifling at this distance, 
were very real at the time. For instance, observation 
on stars for clock rate was usually complicated by a 
temperature of —40*^ with a slight wind, quite sufficient 
to keep one nursing his nose, and to be very careful not 
to put one's eye to the telescope lest it freeze and remain 
there. Other little troubles, such as the stopping of the 
clock by a bodily shift of the wall of the hut upon which 
it was hung, also tended to reduce the accuracy of the 
observations. 
During tlie first winter the pendulum observations 
