208 THE VOYAGE OF THE ' DISCOVERY ' [April 



seen three small instruments, set at different angles, but each 

 containing a delicately suspended magnetic needle to which 

 was attached a tiny mirror ; a shaded lamp and a roll of 

 sensitised photographic paper were so arranged that the light 

 reflected from each small mirror was thrown on to the roll, 

 and the latter was slowly but continuously revolved by clock- 

 work. The sensitised paper came off the roll in long strips, 

 and after being developed exhibited fine wavy lines drawn by 

 the points of light focussed from the mirrors. The three 

 small instruments recorded respectively the declination, hori- 

 zontal force, and vertical force, or the elements of the earth's 

 magnetic pull from which its nature could be calculated at any 

 moment. 



The general reader may well wonder why so much trouble 

 should be taken to ascertain small differences in the earth's 

 magnetism, and he could scarcely be answered in a few words. 

 Broadly speaking, the earth is a magnet, and its magnetism is 

 constantly changing ; but why it is a magnet, or why it 

 changes, or indeed what magnetism may be, is unknown, and 

 obviously the most hopeful road to the explanation of a phe- 

 nomenon is to study it. For many reasons the phenomenon of 

 magnetism could be recorded in few more useful places than 

 our winter station in the Antarctic. 



These record strips were a source of great interest to us all 

 when Bernacchi showed them from time to time. They varied 

 much in character ; sometimes the lines would run with long 

 gradual waves, at others they were distinctly jerky and un- 

 settled, and occasionally, there were magnetic storms when 

 they would fly off the paper altogether. There was a fourth 

 line, which I have not yet mentioned ; this was the line of tem- 

 perature, and was necessary for the correction of the others. 

 It was this that gave Bernacchi most of his trouble and drew 

 to an alarming extent on our oil supply. The desire was to 

 keep a constant temperature inside the hut, but with the 

 frequent change outside this was most difficult to do, and 

 although attempts were made to regulate the burning of a 

 heating lamp within, the variations were at first very great, 



