484 



Scientific Proceedings, Royal Dublin Society. 



current through it, tlie wire could be de-magnetised as far as the vertical 

 component of the Earth's magnetism would permit. 



This was tested by putting a certain current round the solenoid in sucli a 

 way and of such a value as to annul the vertical component of the Earth's 

 magnetism inside it ; and then a current sent through the wire gave little 

 or no twist if the wire was quite de-magnetised. 



The results for five different longitudinal loads on a No. 16 soft-iron 

 wire of cross-sectional area 20-SO X 10"' sq. em., and simple rigidity 

 774 X 10*^ grammes per sq, cm., and electrical conductivity 14'31, are shown in 

 Table II., and as curves in fig. 2. 



Table II. 



■fe 10 



IS 



Fig. 2.— Magnetic Field. 



