242 



GEOMAGNETIC INVESTIGATIONS 



to 1,800 kilograms — the maximum tensile strength of our 12-kilometre 

 cable, allowing a reasonable safety factor of about three — with the result 

 that the thickness of the material would have had to be kept down to a 

 dangerously low minimum. 



This was the position in April 1950, and it looked as though we should 

 either have to abandon our project or be satisfied with containers which 

 would withstand the pressure of only a couple of thousand metres. At this 

 stage a Danish firm sprang to our rescue and succeeded, at very short 

 notice, in producing an entirely new bronze alloy with all the desired 

 qualities. Of course we named it Galathea Bronze. 



The alloy having been produced, the next problem was to get the 

 spheres made in the few months which remained before the expedition's 

 departure. Another Danish firm undertook the work and a third supplied 

 a specially constructed bronze cable to connect the spheres with the long 

 steel wire, so as to prevent the magnetism of this from interfering with 

 the instruments. 



The drawings on page 241 show the single sphere, built to hold either 

 a Z-needle or an //-needle magnetometer, and the double sphere which 

 in the lower space contains the rotating H coil and in the upper the 

 motor (which via an axle through the tube, drives the coil), the amplifier, 

 the recorder, and the necessary accumulators and batteries. The figures 

 on pages 242 — 45 show the spheres in action at various stages. 



H-needle instrument 

 placed in sphere. 



