296 Prof. A. Gray and Mr. A. Wood. Effect of a [May 1, 



whether it changes sign in our specimens at very low amplitudes we 

 are as yet unable to say. 



It will be convenient to give here a short description of the 

 apparatus, and then to state in detail the results obtained from the 

 experiments made on the three substances referred to. The speci- 

 mens were wires about 1 metre long, and about 1*3 mm. in diameter. 

 The exact dimensions are given below where the particular specimens 

 are referred to in the arrangement adopted. The wire is suspended 

 vertically along the axis of a magnetising coil A (Diagram I). Across 

 the upper end of the coil is placed a cross-piece of brass, to which the 

 upper end of the wire is attached, while the coil itself is supported 

 by the upper cross-bar of a Willis frame which stands on the laboratory 



C 



Diagram I. 



floor. About 3 or 4 cm. below the lower end of the coil, the wire is 

 attached to a brass fitting cemented on to the upper end of a glass 



