On the Magnetic Susceptibility of Liquid Oxygen. 315 



Table I. Magnetisation Curves of Tubular Electromagnet, the 

 Induction Density or Field being measured at a point x centi- 

 metres from the Pole Face on the Axial Line. 



The induction density or field along the axial line was also 

 measured for two constant excitations corresponding to currents of 

 12'094 and 6*020 amperes at various distances along the axial line, 

 and the results are given in Table II. 



The results in Tables I and II were then set out carefully in a 

 curve, and from these curves an interpolation table constructed, 

 showing the axial field at various points on the axis for different 

 exciting currents, and these values are given in Table III. 



Having calibrated the magnet, the following objects were provided 

 to be used as bodies to weigh in the field, viz. : 



(1) A silver ball, (2) a rather smaller copper ball, (3) several 

 hollow glass balls containing a little mercury, and (4) a bismuth 

 ball. 



In order to test the method and obtain confidence in the results, we 

 made a number of preliminary measurements on the magnetic suscep- 

 tibility of water, solutions of manganese sulphate, and ferrous sulphate 

 of known densities. 



These experiments were made by weighing the silver ball or hollow 

 glass ball when immersed in these liquids contained in a beaker 

 placed in the field cavity of the magnet. 



Five weighings were always made 



(1) The weight of the ball in air, magnet not excited. 



(2) The apparent weight of the ball in air, magnet excited. 



