CHANGE OF RIGIDITY BT MAGNETIZATION. 



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AA was .1 stout wooden frame rectangular in shape. ?>]î were 

 the parts projecting from the frame ; to the one, a, brass rod, to which 

 a ferromagnetic rod was soldered, was clamped by means of a screw 

 nut H, and to the otlier, a screw G, which carried an agate cup in one 

 of its extremities, was clamped. F was a (hnible pulley whose axis 

 was a thick brass cylinder ; a point made of nonmagnetic nickel steel 

 was iirmly fixed to one of its extremities, wliile the ferromagnetic 

 rod was soldered to the other, as shown in tlie following figure. The 



inner circumference of 

 ] [ r im%m^ the pulley served to 



twist the rod, and the 

 other to multiply the sensibility of the apparatus. C was a mag- 

 netizing coil and E a block of wood, to which a rotating cylinder was 

 affixed as in the case of the former experiment. A fine copper wire, 

 well annealed by passing through it an electric current, was attached 

 to a point on the outer circumference of the pulley and went 

 vertically upward around it. The wire after ]>assing round the 



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