SOUTH 
it could no longer act. Nevertheless, a considerable number of good 
records were obtained, which have not yet been properly worked out. 
Conditions during the Expedition were very favourable for ob- 
servations on the physical properties and natural history of sea-ice, 
and a considerable number of results were obtained, which are, how- 
ever, discussed elsewhere, mention of them being made here since 
they really come under the heading of physics. 
In addition to these main lines of work, many observations of 
a miscellaneous character were made, including those on the occur- 
rence and nature of parhelia or " mock suns," which were very 
common, and generally finely developed, and observations of the 
auroral displays, which were few and rather poor owing to the 
comparatively low magnetic latitude. Since most of the observa- 
tions made are of little value without a knowledge of the place where 
they were made, and since a very complete set of soundings were 
also taken, the daily determination of the ship's position was a 
matter of some importance. The drift of the ship throws consider- 
able Ught on at least one geographical problem, that of the existence 
of Morrell Land. The remainder of this appendix will therefore be 
devoted to a discussion of the methods used to determine the position 
of the ship from day to day. 
The latitude and longitude were determined astronomically 
every day when the sun or stars were visible, the position 
thus determined serving as the fixed points between which the 
position on days when the sky was overcast could be interpo- 
lated by the process known as dead reckoning," that is to say, 
by estimating the speed and course of the ship, taldng into account 
the various causes affecting it. The sky was often overcast for 
several days at a stretch, and it was worth while to take a certain 
amount of care in the matter. Captain Worsley constructed an 
apparatus which gave a good idea of the direction of drift at any 
time. This consisted of an iron rod, which passed through an iron 
tube, frozen vertically into the ice, into the water below. At the 
lower end of the rod, in the water, was a vane. The rod being free 
to turn, the vane took up the direction of the current, the direction 
being shown by an indicator attached to the top of the rod. The 
direction shown depended, of course, on the di'ift of the ice relative 
to the water, and did not take into account any actual current 
which may have been carrying the ice with it, but the true current 
seems never to have been large, and the direction of the vane probablv 
gave fairly accurately the direction of the drift of the ice. No exact 
idea of the rate of drift could be obtained from the apparatus, 
although one could get an estimate of it by displacing the vane from 
its position of rest and noticing how quickly it returned to it, the 
352 
