20 THE ANTARCTIC MANUAL. 
Considering the large areas of open sea which the Discovery will 
probably traverse, and the possibility that cireumstances may even 
prevent the landing of a party on the coast of Victoria Land, observa- 
tions of the magnetic elements at sea are of great importance. It is 
with this view of the value of such observations that the ship has 
been specially designed, and every cause of disturbance from iron 
eliminated within a radius of 30 feet from the centre of the ship’s 
observatory. 
It is further probable that large local magnetic disturbances will be 
found in Victoria Land, in which case there should be no difficulty in 
obtaining normal values on board the ship so prepared as well as on ice. 
For Observations on Land, the instruments furnished comprise: 
(a) Portable Unifilar Magnetometers for determining the absolute 
Horizontal Force and Declination at the base stations. Two. 
(0) Barrow’s Dip Circles (in duplicate) for determining the 
Absolute Dip or Inclination. These circles are provided with 
additional needles for determining the Total Force by Dr. Lloyd’s 
method. These additional needles are never to be reversed or disturbed. 
Deflection bars are also provided for determining the constant depend- 
ing upon the distribution of magnetism in the two needles for force. 
(c) A self-recording apparatus or system of Variometers for regis- 
tering the diurnal variation in the Declination, Horizontal Force, and 
Vertical Force. (Professor Eschenhagen’s system.) 
(d) A special azimuth compass with tripod for observing the 
Declination. It is probable that by using this compass in combina- 
tion with Barrow’s Circle and Lloyd’s needles, the magnetic elements 
may be observed on Antarctic land or ice with greater ease and pre- 
cision than with the Unifilar magnetometer in combination with the 
Dip Circle. 
(¢) Small azimuth compasses, with socket to mount on a tripod 
(in duplicate) for travelling or sledging parties to observe the 
magnetic declination. 
(f) Small compasses (in duplicate) to give direction of travelling 
to sledging parties. 
For Observations on Board Ship, the instruments comprise : 
(a) L. C. * Dip Circle and Intensity Apparatus (in duplicate) for 
determining the Absolute Dip and Relative Intensity at sea or on 
land. This instrument is specially designed for use in either hemi- 
sphere, in regions between the 40th parallels and the geographical 
* Lloyd-Creak., 
