ON MAGNETOSTRICTION, 



attached. The prisai lits in the V-gro(jve, and is fixed tightly hy 

 means of a clamping screw c. To adjust the length he, it is provided 

 with a sHt g. The screw c can be fixed at any part of the slit, and the 

 position of the movable system can be so adjusted that the plane of the 

 lever is perpendicular to the axis of the system. The slight push 

 exerted by the springs s^ s.2 on the movable system prevents the play of 

 différent parts among one another, and was sufficient to overcome 

 friction during the displacement of the system. 



The ovoid was placed inside a solenoid 30 cm. long, which lay in 

 a horizontal position magnetic east and west. The resistance of the 

 solenoid was 0.63 <J, and gave a field of 37.97 C.G.S. units for a cur- 

 rent of one ampere. The internal diameter of the solenoid was 3.2 cm. 

 and no part of the measuring apparatus came in contact with it. 

 Care was taken to place the apparatus along the axis of the solenoid, 

 and so to place the ovoid that its centre coincided with that of the 

 solenoid. 



The optical arrangement for measuring the change of angle of 

 the optical lever is shown in Fig. c. A fine glass thread t is placed 



Fier. c. 



^ 



X. 





W 



vertically in the focus of a collimator c, and illuminated by a gas 

 lamp. The ray after passing the lens, is refiected by a right angled 

 prism 2> attached to the lever. The ray then traverses an achromatic 

 lens L (focal length= 06.95 cm.). The image of the glass thread is 



